Aqueous formulation comprising low visibility naphthalocyanine dye

ABSTRACT

An aqueous formulation comprises a sulfonated water-soluble IR-absorbing naphthalocyanine dye having a central metal atom moiety. A pH of the formulation is in the range of 4 to 6.5, which minimizes visibility of the formulation.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of US Application No. 12694070 filedJan. 26, 2010, which is a continuation of U.S. application Ser. No.11/482,990 filed Jul. 10, 2006, now U.S. Pat. No. 7,658,792, all ofwhich are herein incorporated by reference.

FIELD OF THE INVENTION

The present application relates to infrared (IR) dyes, in particularnear-IR dyes, which are synthetically accessible in high yield and whichare dispersible in an aqueous ink base. It has been developed primarilyfor providing IR inks compatible with CMYK inks, and for optimizing1R-absorption.

CO-PENDING APPLICATIONS

The following applications have been filed by the Applicant with thepresent application:

7,637,588 7,648,222 7,669,958 7,607,755 7,699,433 7,658,463 7,530,6637,467,846 7,669,957 7,771,028 7,758,174 7,695,123 11/482,974 7,604,33411/482,987 7,708,375 7,695,093 7,695,098 7,722,156 7,703,882 7,510,2617,722,153 7,709,633 7,733,535 11/482,967 11/482,966 11/482,988 7,681,0007,530,446 7,654,645 7,784,915 7,571,906 7,703,903 7,645,034 7,637,6027,645,033

The disclosures of these co-pending applications are incorporated hereinby reference.

CROSS REFERENCES TO RELATED APPLICATIONS

Various methods, systems and apparatus relating to the present inventionare disclosed in the following US patents/patent applications filed bythe applicant or assignee of the present invention:

6,750,901 6,476,863 6,788,336 7,249,108 6,566,858 6,331,946 6,246,9706,442,525 7,346,586 7,685,423 6,374,354 7,246,098 6,816,968 6,757,8326,334,190 6,745,331 7,249,109 7,197,642 7,093,139 7,509,292 7,685,4247,743,262 7,210,038 7,401,223 7,702,926 7,716,098 7,364,256 7,258,4177,293,853 7,328,968 7,270,395 7,461,916 7,510,264 7,334,864 7,255,4197,284,819 7,229,148 7,258,416 7,273,263 7,270,393 6,984,017 7,347,5267,357,477 7,465,015 7,364,255 7,357,476 7,758,148 7,284,820 7,341,3287,246,875 7,322,669 7,445,311 7,452,052 7,455,383 7,448,724 7,441,8647,506,958 7,472,981 7,448,722 7,575,297 7,438,381 7,441,863 7,438,3827,425,051 7,399,057 7,695,097 7,686,419 7,753,472 7,448,720 7,448,7237,445,310 7,399,054 7,425,049 7,367,648 7,370,936 7,401,886 7,506,9527,401,887 7,384,119 7,401,888 7,387,358 7,413,281 7,243,835 10/815,6307,703,693 10/815,638 7,251,050 10/815,642 7,097,094 7,137,549 10/815,6187,156,292 10/815,635 7,357,323 7,654,454 7,137,566 7,131,596 7,128,2657,207,485 7,197,374 7,175,089 10/815,617 7,537,160 7,178,719 7,506,8087,207,483 7,296,737 7,270,266 7,605,940 7,128,270 7,784,681 7,677,4457,506,168 7,441,712 7,663,789 11/041,609 11/041,626 7,537,157 11/041,6247,395,963 7,457,961 7,739,509 7,467,300 7,467,299 7,565,542 7,457,0077,150,398 7,159,777 7,450,273 7,188,769 7,097,106 7,070,110 7,243,8496,623,101 6,406,129 6,505,916 6,457,809 6,550,895 6,457,812 7,152,9626,428,133 7,204,941 7,282,164 7,465,342 7,278,727 7,417,141 7,452,9897,367,665 7,138,391 7,153,956 7,423,145 7,456,277 7,550,585 7,122,0767,148,345 7,470,315 7,572,327 7,416,280 7,252,366 7,488,051 7,360,8657,438,371 7,465,017 7,441,862 7,654,636 7,458,659 7,455,376 6,746,1057,744,195 7,645,026 7,322,681 7,708,387 7,753,496 7,712,884 7,510,2677,465,041 11/246,712 7,465,032 7,401,890 7,401,910 7,470,010 7,735,9717,431,432 7,465,037 7,445,317 7,549,735 7,597,425 7,661,800 7,712,8697,156,508 7,159,972 7,083,271 7,165,834 7,080,894 7,201,469 7,090,3367,156,489 7,413,283 7,438,385 7,083,257 7,258,422 7,255,423 7,219,9807,591,533 7,416,274 7,367,649 7,118,192 7,618,121 7,322,672 7,0775057,198,354 7,077,504 7,614,724 7,198,355 7,401,894 7,322,676 7,152,9597,213,906 7,178,901 7,222,938 7,108,353 7,104,629 7,303,930 7,401,4057,464,466 7,464,465 7,246,886 7,128,400 7,108,355 6,991,322 7,287,8367,118,197 7,575,298 7,364,269 7,077,493 6,962,402 7,686,429 7,147,3087,524,034 7,118,198 7,168,790 7,172,270 7,229,155 6,830,318 7,195,3427,175,261 7,465,035 7,108,356 7,118,202 7,510,269 7,134,744 7,510,2707,134,743 7,182,439 7,210,768 7,465,036 7,134,745 7,156,484 7,118,2017,111,926 7,431,433 7,018,021 7,401,901 7,468,139 7,128,402 7,387,3697,484,832 7,448,729 7,246,876 7,431,431 7,419,249 7,377,623 7,328,9787,334,876 7,147,306 7,466,440 7,249,901 7,477,987 7,503,493 7,156,2897,178,718 7,225,979 7,540,429 7,584,402 11/084,806 7,721,948 7,079,7126,825,945 7,330,974 6,813,039 7,190,474 6,987,506 6,824,044 7,038,7976,980,318 6,816,274 7,102,772 7,350,236 6,681,045 6,678,499 6,679,4206,963,845 6,976,220 6,728,000 7,110,126 7,173,722 6,976,035 6,813,5586,766,942 6,965,454 6,995,859 7,088,459 6,720,985 7,286,113 6,922,7796,978,019 6,847,883 7,131,058 7,295,839 7,406,445 7,533,031 6,959,2986,973,450 7,150,404 6,965,882 7,233,924 7,707,082 7,593,899 7,175,0797,162,259 6,718,061 7,464,880 7,012,710 6,825,956 7,451,115 7,222,0987,590,561 7,263,508 7,031,010 6,972,864 6,862,105 7,009,738 6,989,9116,982,807 7,518,756 6,829,387 6,714,678 6,644,545 6,609,653 6,651,87910/291,555 7,293,240 7,467,185 7,415,668 7,044,363 7,004,390 6,867,8807,034,953 6,987,581 7,216,224 7,506,153 7,162,269 7,162,222 7,290,2107,293,233 7,293,234 6,850,931 6,865,570 6,847,961 10/685,583 7,162,44210/685,584 7,159,784 7,557,944 7,404,144 6,889,896 7,174,056 6,996,2747,162,088 7,388,985 7,417,759 7,362,463 7,259,884 7,167,270 7,388,6856,986,459 10/954,170 7,181,448 7,590,622 7,657,510 7,324,989 7,231,2937,174,329 7,369,261 7,295,922 7,200,591 7,693,828 11/020,260 11/020,32111/020,319 7,466,436 7,347,357 11/051,032 7,382,482 7,602,515 7,446,89311/082,815 7,389,423 7,401,227 6,991,153 6,991,154 7,589,854 7,551,3057,322,524 7,408,670 7,466,439 11/206,778 7,571,193 11/222,977 7,327,4857,428,070 7,225,402 11/349,143 7,068,382 7,007,851 6,957,921 6,457,8837,044,381 11/203,205 7,094,910 7,091,344 7,122,685 7,038,066 7,099,0197,062,651 6,789,194 6,789,191 7,529,936 7,278,018 7,360,089 7,526,6477,467,416 6,644,642 6,502,614 6,622,999 6,669,385 6,827,116 7,011,1287,416,009 6,549,935 6,987,573 6,727,996 6,591,884 6,439,706 6,760,1197,295,332 7,064,851 6,826,547 6,290,349 6,428,155 6,785,016 6,831,6826,741,871 6,927,871 6,980,306 6,965,439 6,840,606 7,036,918 6,977,7466,970,264 7,068,389 7,093,991 7,190,491 7,511,847 7,663,780 10/962,4127,177,054 7,364,282 10/965,733 10/965,933 7,728,872 7,468,809 7,180,6097,538,793 7,466,438 7,292,363 7,515,292 7,414,741 7,202,959 6,982,7986,870,966 6,822,639 6,474,888 6,627,870 6,724,374 6,788,982 7,263,2706,788,293 6,946,672 6,737,591 7,091,960 7,369,265 6,792,165 7,105,7536,795,593 6,980,704 6,768,821 7,132,612 7,041,916 6,797,895 7,015,9017,289,882 7,148,644 10/778,056 10/778,058 7,515,186 7,567,279 10/778,0627,096,199 7,286,887 7,400,937 7,474,930 7,324,859 7,218,978 7,245,2947,277,085 7,187,370 7,609,410 7,660,490 10/919,379 7,019,319 7,593,6047,660,489 7,043,096 7,148,499 7,463,250 7,590,311 11/155,557 11/193,4817,567,241 11/193,482 11/193,479 7,336,267 7,388,221 7,577,317 7,055,7397,233,320 6,830,196 6,832,717 7,182,247 7,120,853 7,082,562 6,843,42010/291,718 6,789,731 7,057,608 6,766,944 6,766,945 7,289,103 7,412,6517,299,969 7,264,173 7,108,192 7,549,595 7,111,791 7,077,333 6,983,8787,564,605 7,134,598 7,431,219 6,929,186 6,994,264 7,017,826 7,014,1237,134,601 7,150,396 7,469,830 7,017,823 7,025,276 7,284,701 7,080,7807,376,884 10/492,169 7,469,062 7,359,551 7,444,021 7,308,148 7,630,96210/531,229 7,630,553 7,630,554 10/510,391 7,660,466 7,526,128 6,957,7687,456,820 7,170,499 7,106,888 7,123,239 6,982,701 6,982,703 7,227,5276,786,397 6,947,027 6,975,299 7,139,431 7,048,178 7,118,025 6,839,0537,015,900 7,010,147 7,133,557 6,914,593 7,437,671 6,938,826 7,278,5667,123,245 6,992,662 7,190,346 7,417,629 7,468,724 7,382,354 7,715,0357,221,781 11/102,843 7,263,225 10/727,162 7,377,608 7,399,043 7,121,6397,165,824 7,152,942 10/727,157 7,181,572 7,096,137 7,302,592 7,278,0347,188,282 7,592,829 10/727,179 10/727,192 7,770,008 7,707,621 7,523,1117,573,301 7,660,998 7,783,886 10/754,938 10/727,160 7,171,323 7,278,6977,369,270 6,795,215 7,070,098 7,154,638 6,805,419 6,859,289 6,977,7516,398,332 6,394,573 6,622,923 6,747,760 6,921,144 7,092,112 7,192,1067,457,001 7,173,739 6,986,560 7,008,033 7,551,324 7,222,780 7,270,3917,195,328 7,182,422 7,374,266 7,427,117 7,448,707 7,281,330 10/854,5037,328,956 7,735,944 7,188,928 7,093,989 7,377,609 7,600,843 10/854,4987,390,071 10/854,526 7,549,715 7,252,353 7,607,757 7,267,417 10/854,5057,517,036 7,275,805 7,314,261 7,281,777 7,290,852 7,484,831 7,758,14310/854,527 7,549,718 10/854,520 7,631,190 7,557,941 7,757,086 10/854,5017,266,661 7,243,193 10/854,518 7,163,345 7,465,033 7,452,055 7,470,0027,722,161 7,475,963 7,448,735 7,465,042 7,448,739 7,438,399 11/293,7947,467,853 7,461,922 7,465,020 7,722,185 7,461,910 7,270,494 7,632,0327,475,961 7,547,088 7,611,239 7,735,955 7,758,038 7,681,876 7,780,1617,448,734 7,425,050 7,364,263 7,201,468 7,360,868 7,234,802 7,303,2557,287,846 7,156,511 10/760,264 7,258,432 7,097,291 7,645,025 10/760,2487,083,273 7,367,647 7,374,355 7,441,880 7,547,092 10/760,206 7,513,59810/760,270 7,198,352 7,364,264 7,303,251 7,201,470 7,121,655 7,293,8617,232,208 7,328,985 7,344,232 7,083,272 7,621,620 7,669,961 7,331,6637,360,861 7,328,973 7,427,121 7,407,262 7,303,252 7,249,822 7,537,3097,311,382 7,360,860 7,364,257 7,390,075 7,350,896 7,429,096 7,384,1357,331,660 7,416,287 7,488,052 7,322,684 7,322,685 7,311,381 7,270,4057,303,268 7,470,007 7,399,072 7,393,076 7,681,967 7,588,301 7,249,8337,524,016 7,490,927 7,331,661 7,524,043 7,300,140 7,357,492 7,357,4937,566,106 7,380,902 7,284,816 7,284,845 7,255,430 7,390,080 7,328,9847,350,913 7,322,671 7,380,910 7,431,424 7,470,006 7,585,054 7,347,5347,441,865 7,469,989 7,367,650 7,469,990 7,441,882 7,556,364 7,357,4967,467,863 7,431,440 7,431,443 7,527,353 7,524,023 7,513,603 7,467,8526,454,482 6,808,330 6,527,365 6,474,773 6,550,997 7,093,923 6,957,9237,131,724 7,396,177 7,168,867 7,125,098 7,413,363 7,188,930

BACKGROUND OF THE INVENTION

IR absorbing dyes have numerous applications, such as optical recordingsystems, thermal writing displays, laser filters, infrared photography,medical applications and printing. Typically, it is desirable for thedyes used in these applications to have strong absorption in the near-IRat the emission wavelengths of semiconductor lasers (e.g. between about700 and 2000 nm, preferably between about 700 and 1000 nm). In opticalrecording technology, for example, gallium aluminium arsenide (GaAlAs)and indium phosphide (InP) diode lasers are widely used as lightsources.

Another important application of IR dyes is in inks, such as printinginks. The storage and retrieval of digital information in printed formis particularly important. A familiar example of this technology is theuse of printed, scannable bar codes. Bar codes are typically printedonto tags or labels associated with a particular product and containinformation about the product, such as its identity, price etc. Barcodes are usually printed in lines of visible black ink, and detectedusing visible light from a scanner. The scanner typically comprises anLED or laser (e.g. a HeNe laser, which emits light at 633 nm) lightsource and a photocell for detecting reflected light. Black dyessuitable for use in barcode inks are described in, for example,WO03/074613.

However, in other applications of this technology (e.g. securitytagging) it is desirable to have a barcode, or other intelligiblemarking, printed with an ink that is invisible to the unaided eye, butwhich can be detected under UV or IR light.

An especially important application of detectable invisible ink is inautomatic identification systems, and especially “netpage” and“Hyperlabel™” systems. Netpage systems are the subject of a number ofpatents and patent applications some of which are listed in thecross-reference section above and, all of which are incorporated hereinby reference.

In general, the netpage system relies on the production of, and humaninteraction with, netpages. These are pages of text, graphics and imagesprinted on ordinary paper, but which work like interactive web pages.Information is encoded on each page using ink which is substantiallyinvisible to the unaided human eye. The ink, however, and thereby thecoded data, can be sensed by an optically imaging pen and transmitted tothe netpage system.

Active buttons and hyperlinks on each page may be clicked with the pento request information from the network or to signal preferences to anetwork server. In some forms, text written by hand on a netpage may beautomatically recognized and converted to computer text in the netpagesystem, allowing forms to be filled in. In other forms, signaturesrecorded on a netpage may be automatically verified, allowing e-commercetransactions to be securely authorized.

Netpages are the foundation on which a netpage network is built. Theymay provide a paper-based user interface to published information andinteractive services.

A netpage consists of a printed page (or other surface region) invisiblytagged with references to an online description of the page. The onlinepage description is maintained persistently by a netpage page server.The page description describes the visible layout and content of thepage, including text, graphics and images. It also describes the inputelements on the page, including buttons, hyperlinks, and input fields. Anetpage allows markings made with a netpage pen on its surface to besimultaneously captured and processed by the netpage system.

Multiple netpages can share the same page description. However, to allowinput through otherwise identical pages to be distinguished, eachnetpage is assigned a unique page identifier. This page ID hassufficient precision to distinguish between a very large number ofnetpages.

Each reference to the page description is encoded in a printed tag. Thetag identifies the unique page on which it appears, and therebyindirectly identifies the page description. The tag also identifies itsown position on the page.

Tags are printed in infrared-absorptive ink on any substrate which isinfrared-reflective, such as ordinary paper. Near-infrared wavelengthsare invisible to the human eye but are easily sensed by a solid-stateimage sensor with an appropriate filter.

A tag is sensed by an area image sensor in the netpage pen, and the tagdata is transmitted to the netpage system via the nearest netpageprinter. The pen is wireless and communicates with the netpage printervia a short-range radio link. Tags are sufficiently small and denselyarranged that the pen can reliably image at least one tag even on asingle click on the page. It is important that the pen recognize thepage ID and position on every interaction with the page, since theinteraction is stateless. Tags are error-correctably encoded to makethem partially tolerant to surface damage.

The netpage page server maintains a unique page instance for eachprinted netpage, allowing it to maintain a distinct set of user-suppliedvalues for input fields in the page description for each printednetpage.

Hyperlabel™ is a trade mark of Silverbrook Research Pty Ltd, Australia.In general, Hyperlabel™ systems use an invisible (e.g. infrared) taggingscheme to uniquely identify a product item. This has the significantadvantage that it allows the entire surface of a product to be tagged,or a significant portion thereof, without impinging on the graphicdesign of the product's packaging or labeling. If the entire surface ofa product is tagged (“omnitagged”), then the orientation of the productdoes not affect its ability to be scanned i.e. a significant part of theline-of-sight disadvantage of visible barcodes is eliminated.Furthermore, if the tags are compact and massively replicated(“omnitags”), then label damage no longer prevents scanning.

Thus, hyperlabelling consists of covering a large portion of the surfaceof a product with optically-readable invisible tags. When the tagsutilize reflection or absorption in the infrared spectrum, they arereferred to as infrared identification (IRID) tags. Each Hyperlabel™ taguniquely identifies the product on which it appears. The tag maydirectly encode the product code of the item, or it may encode asurrogate ID which in turn identifies the product code via a databaselookup. Each tag also optionally identifies its own position on thesurface of the product item, to provide the downstream consumer benefitsof netpage interactivity.

Hyperlabels™ are applied during product manufacture and/or packagingusing digital printers, preferably inkjet printers. These may be add-oninfrared printers, which print the tags after the text and graphics havebeen printed by other means, or integrated colour and infrared printerswhich print the tags, text and graphics simultaneously.

Hyperlabels™ can be detected using similar technology to barcodes,except using a light source having an appropriate near-IR frequency. Thelight source may be a laser (e.g. a GaAlAs laser, which emits light at830 nm) or it may be an LED.

From the foregoing, it will be readily apparent that invisible IRdetectable inks are an important component of netpage and Hyperlabel™systems. In order for an IR absorbing ink to function satisfactorily inthese systems, it should ideally meet a number of criteria:

(i) compatibility of the IR dye with traditional inkjet inks;

(ii) compatibility of the IR dye with aqueous solvents used in inkjetinks;

(iii) intense absorption in the near infra-red region (e.g. 700 to 1000nm);

(iv) zero or low intensity visible absorption;

(v) lightfastness;

(vi) thermal stability;

(vii) zero or low toxicity;

(viii) low-cost manufacture;

(ix) adheres well to paper and other media; and

(x) no strikethrough and minimal bleeding of the ink on printing.

Hence, it would be desirable to develop IR dyes and ink compositionsfulfilling at least some and preferably all of the above criteria. Suchinks are desirable to complement netpage and Hyperlabel™ systems.

Some IR dyes are commercially available from various sources, such asEpolin Products, Avecia Inks and H.W. Sands Corp.

In addition, the prior art describes various IR dyes. U.S. Pat. No.5,460,646, for example, describes an infrared printing ink comprising acolorant, a vehicle and a solvent, wherein the colorant is a silicon(IV) 2,3-naphthalocyanine bis-trialkylsilyloxide.

U.S. Pat. No. 5,282,894 describes a solvent-based printing inkcomprising a metal-free phthalocyanine, a complexed phthalocyanine, ametal-free naphthalocyanine, a complexed naphthalocyanine, a nickeldithiolene, an aminium compound, a methine compound or an azulenesquaricacid.

However, none of these prior art dyes can be formulated into inkcompositions suitable for use in netpage or Hyperlabel™ systems. Inparticular, commercially available and/or prior art inks suffer from oneor more of the following problems: absorption at wavelengths unsuitablefor detection by near-IR sensors; poor solubility or dispersibility inaqueous solvent systems; or unacceptably high absorption in the visiblepart of the spectrum.

In our earlier U.S. patent application Ser. No. 10/986,402 (the contentsof which is herein incorporated by reference), we described awater-soluble gallium naphthalocyanine dye fulfilling many of thedesirable properties identified above. The dye typically comprises foursulfonic acid groups, which impart a high degree of water-solubility,either in its acid or salt form. However, it has since been found thatthe formation of salts using, for example, sodium hydroxide ortriethylamine produces an unexpected blue-shift in the Q-band (λ_(max))of the dye, from about 805 nm to about 790 nm or less. On the one hand,salt formation is desirable because it raises the pH of the dye insolution making it compatible with other CMYK inks. Typically, CMYK inkshave a pH in the range of 8-9, so a strongly acidic IR ink wouldpotentially cause precipitation of ink components if the IR and CMYKinks are mixed on a printhead face during purging. On the other hand,blue-shifting of the Q-band caused by salt formation makes these dyesless appealing as IR ink candidates, because they must be used in higherconcentrations to have acceptable detectability by an IR sensor,resulting in the ink appearing more colored.

These contradictory requirements of the IR dye need to be addressed inorder to formulate an IR ink having optimal performance in netpage andHyperlabel™ applications.

SUMMARY OF THE INVENTION

In a first aspect, there is provided an IR-absorbing naphthalocyaninedye of formula (I):

wherein:

M is Ga(A¹);

A¹ is an axial ligand selected from —OH, halogen, —OR³, —OC(O)R⁴ or—O(CH₂CH₂O)_(c)R^(e) wherein e is an integer from 2 to 10 and R^(e) isH, C₁₋₈ alkyl or C(O)C₁₋₈ alkyl;R¹ and R² may be the same or different and are selected from hydrogen orC₁₋₁₂ alkoxy;R³ is selected from C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl orSi(R^(x))(R^(y))(R^(z));R⁴ is selected from C₁₋₁₂ alkyl, C₅₋₁₂ aryl or C₅₋₁₂ arylalkyl;R^(x), R^(y) and R^(z) may be the same or different and are selectedfrom C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl, C₁₋₁₂ alkoxy, C₅₋₁₂aryloxy or C₅₋₁₂ arylalkoxy; andeach B is independently selected from a base, wherein BH⁺ has a pK_(a)of between 4 and 9.

Alternatively, there is provided an aqueous formulation comprising anIR-absorbing naphthalocyanine dye of formula (II):

or a salt form thereof, wherein:

M is Ga(A¹);

A¹ is an axial ligand selected from —OH, halogen, —OR³, —OC(O)R⁴ or—O(CH₂CH₂O)_(c)R^(e) wherein e is an integer from 2 to 10 and R^(e) isH, C₁₋₈ alkyl or C(O)C₁₋₈ alkyl;R¹ and R² may be the same or different and are selected from hydrogen orC₁₋₁₂ alkoxy;R³ is selected from C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl orSi(R^(x))(R^(y))(R^(z));R⁴ is selected from C₁₋₁₂ alkyl, C₅₋₁₂ aryl or C₅₋₁₂ arylalkyl; andR^(x), R^(y) and R^(z) may be the same or different and are selectedfrom C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl, C₁₋₁₂ alkoxy, C₅₋₁₂aryloxy or C₅₋₁₂ arylalkoxy;said formulation having a pH in the range of 3.5 to 7.

In a second aspect, there is provided an inkjet ink comprising a dye ora formulation as described above.

In a third aspect, there is provided an inkjet printer comprising aprinthead in fluid communication with at least one ink reservoir,wherein said at least one ink reservoir comprises an inkjet ink asdescribed above.

In a fourth aspect, there is provided an ink cartridge for an inkjetprinter, wherein said ink cartridge comprises an inkjet ink as describedabove.

In a fifth aspect, there is provided a substrate having a dye asdescribed above disposed thereon.

In a sixth aspect, there is provided a method of enabling entry of datainto a computer system via a printed form, the form containinghuman-readable information and machine-readable coded data, the codeddata being indicative of an identity of the form and of a plurality oflocations on the form, the method including the steps of:

receiving, in the computer system and from a sensing device, indicatingdata regarding the identity of the form and a position of the sensingdevice relative to the form, the sensing device, when placed in anoperative position relative to the form, generating the indicating datausing at least some of the coded data;

identifying, in the computer system and from the indicating data, atleast one field of the form; and

interpreting, in the computer system, at least some of the indicatingdata as it relates to the at least one field,

wherein said coded data comprises an IR-absorbing dye as describedabove.

In a seventh aspect, there is provided a method of interacting with aproduct item, the product item having a printed surface containinghuman-readable information and machine-readable coded data, the codeddata being indicative of an identity of the product item, the methodincluding the steps of:

(a) receiving, in the computer system and from a sensing device,indicating data regarding the identity of the product item, the sensingdevice, when placed in an operative position relative to the productitem, generating the indicating data using at least some of the codeddata; and(b) identifying, in the computer system and using the indicating data,an interaction relating to the product item,wherein said coded data comprises an IR-absorbing dye according asdescribed above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic of a the relationship between a sample printednetpage and its online page description;

FIG. 2 is a schematic view of a interaction between a netpage pen, a Webterminal, a netpage printer, a netpage relay, a netpage page server, anda netpage application server, and a Web server;

FIG. 3 illustrates a collection of netpage servers, Web terminals,printers and relays interconnected via a network;

FIG. 4 is a schematic view of a high-level structure of a printednetpage and its online page description;

FIG. 5A is a plan view showing the interleaving and rotation of thesymbols of four codewords of the tag;

FIG. 5B is a plan view showing a macrodot layout for the tag shown inFIG. 5A;

FIG. 5C is a plan view showing an arrangement of nine of the tags shownin FIGS. 5 a and 5 b, in which targets are shared between adjacent tags;

FIG. 5D is a plan view showing a relationship between a set of the tagsshown in FIG. 5 a and a field of view of a netpage sensing device in theform of a netpage pen;

FIG. 6 is a perspective view of a netpage pen and its associatedtag-sensing field-of-view cone;

FIG. 7 is a perspective exploded view of the netpage pen shown in FIG.6;

FIG. 8 is a schematic block diagram of a pen controller for the netpagepen shown in FIGS. 6 and 7;

FIG. 9 is a perspective view of a wall-mounted netpage printer;

FIG. 10 is a section through the length of the netpage printer of FIG.9;

FIG. 10A is an enlarged portion of FIG. 10 showing a section of theduplexed print engines and glue wheel assembly;

FIG. 11 is a detailed view of the ink cartridge, ink, air and gluepaths, and print engines of the netpage printer of FIGS. 9 and 10;

FIG. 12 is an exploded view of an ink cartridge;

FIG. 13 is a schematic view of the structure of an item ID;

FIG. 14 is a schematic view of the structure of an omnitag;

FIG. 15 is a schematic view of a pen class diagram;

FIG. 16 is a schematic view of the interaction between a product item, afixed product scanner, a hand-held product scanner, a scanner relay, aproduct server, and a product application server;

FIG. 17 is a perspective view of a bi-lithic printhead;

FIG. 18 an exploded perspective view of the bi-lithic printhead of FIG.17;

FIG. 19 is a sectional view through one end of the bi-lithic printheadof FIG. 17;

FIG. 20 is a longitudinal sectional view through the bi-lithic printheadof FIG. 17;

FIGS. 21(A) to 21(D) show a side elevation, plan view, opposite sideelevation and reverse plan view, respectively, of the bi-lithicprinthead of FIG. 17;

FIGS. 22(A) to 22(C) show the basic operational principles of a thermalbend actuator;

FIG. 23 shows a three dimensional view of a single ink jet nozzlearrangement constructed in accordance with FIG. 22;

FIG. 24 shows an array of the nozzle arrangements shown in FIG. 23;

FIG. 25 is a schematic cross-sectional view through an ink chamber of aunit cell of a bubble forming heater element actuator;

FIG. 26 shows a reflectance spectrum of hydroxygalliumnaphthalocyaninetetrasulfonic acid 4;

FIG. 27 shows a ¹H NMR spectrum of hydroxygalliumnaphthalocyaninetetrasulfonic acid 4 in d₆-DMSO (0.1% w/v);

FIG. 28 shows a reflectance spectrum of tetraimidazolium hydroxygalliumnaphthalocyaninetetrasulfonate 7;

FIG. 29 shows a reflectance spectrum of tetrakis(DBUammonium)hydroxygallium naphthalocyaninetetrasulfonate 9;

FIG. 30 shows a reflectance spectrum of tetrakis(DBUammonium)hydroxygallium naphthalocyaninetetrasulfonate 9 with p-toluenesulfonicacid (3 equivalents);

FIG. 31 shows a reflectance spectrum of tetraimidazolium hydroxygalliumnaphthalocyaninetetrasulfonate 7 with two equivalents of acetic acid.

DETAILED DESCRIPTION IR-Absorbing Dye

As used herein, the term “IR-absorbing dye” means a dye substance, whichabsorbs infrared radiation and which is therefore suitable for detectionby an infrared sensor. Preferably, the IR-absorbing dye absorbs in thenear infrared region, and preferably has a λ_(max) in the range of 700to 1000 nm, more preferably 750 to 900 nm, more preferably 780 to 850nm. Dyes having a λ_(max) in this range are particularly suitable fordetection by semiconductor lasers, such as a gallium aluminium arsenidediode laser.

As will be explained in more detail below, dyes represented by formula(I) may be in equilibrium with other tautomers in which meso-nitrogen(s)of the naphthalocyanine ring system are protonated. Indeed, the dyerepresented by formula (I) may only be a minor species in thisequilibrium. However, by convention, dyes according to the presentinvention are generally represented by formula (I). Other tautomers inequilibrium therewith are, of course, included within the scope of thepresent invention.

Dyes according to the present invention have the advantageous featuresof: optimal absorption in the near-IR region; suitability forformulation into aqueous inkjet inks; pH compatible with known CMYK inkswithout sacrificing optimal near-IR absorption; and facile preparation.Moreover, their high extinction coefficients in the near-IR region meansthat the dyes appear “invisible” at a concentration suitable fordetection by a near-IR detector (e.g. a netpage pen). Accordingly, thedyes of the present invention are especially suitable for use in netpageand Hyperlabel™ applications. None of the dyes known in the prior arthas this unique combination of properties.

The present invention was initially conceived by observing the reactionof a gallium naphthalocyanine tetrasulfonic acid salt with fourequivalents of amine to given an ammonium salt. It was found,surprisingly, that the reflectance spectra of ammonium salts areindependent of the structure of the amine, but very much affected by thepK_(a) of the ammonium salt. At low pK_(a) the Q-band (λ_(max)) has alarge monomeric component and is red-shifted to 800-810 nm. However,when strongly basic amines are used, the Q-band exhibits a significantdimer or aggregate component and the monomer component is blue shiftedto <800 nm. Given that the internal meso nitrogens of thenaphthalocyanine ring system have pK_(a) values of about 11.5 (firstprotonation) and 6.7 (second protonation), then without wishing to bebound by theory, these results have been interpreted in terms of theability of the ammonium ion to protonate zero (structure A), one(structure B) or two (structure C) of the meso nitrogens. The greaterthe protonating ability of the ammonium ion (lower pKa), the greater thedegree of protonation of the macrocycle. It is believed that protonationof the macrocycle reduces π-π stacking between adjacent molecules byelectrostatic repulsion. With less aggregation and a greater monomercomponent, a red-shift of the Q-band of the salt is observed.

Following on from these surprising results, it was then found that otherweak acids could effect the same phenomena. For example, treating thetetrasulfonic acid with four equivalents of lithium or sodium acetate(B═AcO⁻) gave characteristic red-shifted spectra resulting from theformation of the lithium or sodium salt and four equivalents of aceticacid. It was therefore concluded that the pH of the solution (controlledby the pK_(a) of the BH⁺ species) is the most important factor incontrolling the red-shifted behaviour of certain naphthalocyanine dyes.

With pH identified as the key factor controlling λ_(max), it followsthat suitable IR ink formulations may be prepared by dissolving anaphthalocyaninetetrasulfonic acid in an ink vehicle and adjusting thepH of the resulting formulation. It has been found that formulationshaving a pH within the range of 3.5 to 7, or optionally 4 to 6.5, aredesirable for achieving a red-shifted Q-band while maintaining CMYKcompatibility. The pH may be adjusted using any suitable base (e.g. theconjugate bases of the weak acids described below) or using a buffersolution.

It is expected that the same phenomenon may be similarly used incontrolling Q-band absorption for a whole range of sulfonatedphthalocyanine and naphthalocyanine dyes. The use of pH to fine-tuneQ-band absorption has not been exploited previously and represents aconvenient, low cost approach to producing red-shifted IR dyes. Specificexamples of dyes and formulations exploiting this phenomenon areprovided below in the Examples.

The species BH⁺ in the present invention is a weak acid having a pK_(a)in the range of 4 to 9, or optionally 4.5 to 8. The dyes of formula (I)may be readily formed by the addition of a base to the correspondingtetrasulfonic acid. The base B may be neutral (e.g. pyridine), in whichcase BH⁺ will be overall positively charged (e.g. C₆H₅NH⁺).Alternatively, the base may be anionic (e.g. acetate anion) in whichcase BH⁺ will be overall neutral (e.g. AcOH). In the case of any or allof BH⁺ being neutral, the overall neutrality of the naphthalocyaninesalt is maintained by a suitable number of metal counterions (e.g. Li⁺,Na⁺ etc).

The skilled person will be well aware of a wide variety of weak acids,which fulfil the criteria of the present invention. Some examples ofcommon acids having a pK_(a) in the range of 4 to 9 are provided below.In accordance with convention, the pK_(a) of some acids are referred toby their corresponding conjugate base. For example, the pK_(a) ofpyridine refers to the pK_(a) of the corresponding pyridinium ion.

Acetic acid 4.76 Ethyleneimine 8.01 1H-Imidazole 6.95 2-Thiazolamine5.36 Acrylic acid 4.25 Melamine 5.00 Propanoic acid 4.863-Hydroxypropanoic acid 4.51 Trimethylamine oxide 4.65 Barbituric acid4.01 Alloxanic acid 6.64 1-Methylimidazole 6.95 Allantoin 8.963-Butenoic acid 4.34 trans-Crotonic acid 4.69 3-Chlorobutanoic acid 4.054-Chlorobutanoic acid 4.52 Butanoic acid 4.83 2-Methylpropanoic acid4.88 3-Hydroxybutanoic acid 4.70 4-Hydroxybutanoic acid 4.72 Morpholine8.33 Pyridine 5.25 2-Pyridinamine 6.82 2,5-Pyridinediamine 6.482,4-Dimethylimidazole 8.36 Methylsuccinic acid 4.13 Histamine 6.04; 9.752-Methylbutanoic acid 4.80 3-Methylbutanoic acid 4.77 Pentanoic acid4.84 Trimethylacetic acid 5.03 2,3-Dichlorophenol 7.44 3,6-Dinitrophenol5.15 Pteridine 4.05 2-Chlorophenol 8.49 3-Chlorophenol 8.853-Pyridinecarboxylic acid 4.85 4-Pyridinecarboxylic acid 4.962-Nitrophenol 7.17 3-Nitrophenol 8.28 4-Nitrophenol 7.15 4-Chloroaniline4.15 4-Fluoroaniline 4.65 Aniline 4.63 2-Methylpyridine 5.973-Methylpyridine 5.68 4-Methylpyridine 6.02 Methoxypyridine 6.474,6-Dimethylpyrimidinamine 4.82 3-Methylglutaric acid 4.24 Adiparnicacid 4.63 Hexanoic acid 4.85 4-Methylpentanoic acid 4.84 Benzimidazole5.53 Benzoic acid 4.19 3,5-Dihydroxybenzoic acid 4.04 Gallic acid 4.413-Aminobenzoic acid 4.78 2,3-Dimethylpyridine 6.57 2,4-Dimethylpyridine6.99 2,5-Dimethylpyridine 6.40 2,6-Dimethylpyridine 6.653,4-Dimethylpyridine 6.46 3,5-Dimethylpyridine 6.15 2-Ethylpyridine 5.89N-Methylaniline 4.84 o-Methylaniline 4.44 m-Methylaniline 4.73p-Methylaniline 5.08 o-Anisidine 4.52 m-Anisidine 4.23 p-Anisidine 5.344-Methylthioaniline 4.35 Cyclohexanecarboxylic acid 4.90 Heptanoic acid4.89 2-Methylbenzimidazole 6.19 Phenylacetic acid 4.282-(Methylamino)benzoic acid 5.34 3-(Methylamino)benzoic acid 5.104-(Methylamino)benzoic acid 5.04 N,N-Dimethylaniline 5.15 N-Ethylaniline5.12 2,4,6-Trimethylpyridine 7.43 o-Phenetidine 4.43 m-Phenetidine 4.18p-Phenetidine 5.20 Veronal 7.43 Octanedioic acid 4.52 Octanoic acid 4.89o-Chlorocinnamic acid 4.23 m-Chlorocinnamic acid 4.29 p-Chlorocinnamicacid 4.41 Isoquinoline 5.42 Quinoline 4.90 7-Isoquinolinol 5.681-Isoquinolinamine 7.59 3-Quinolinamine 4.91 trans-Cinnamic acid 4.442-Ethylbenzimidazole 6.18 Mesitylenic acid 4.32 N-Allylaniline 4.17Tyrosineamide 7.33 Nonanic acid 4.96 2-Methylquinoline 5.834-Methylquinoline 5.67 5-Methylquinoline 5.20 6-Methoxyquinoline 5.03o-Methylcinnamic acid 4.50 m-Methylcinnamic acid 4.44 p-Methylcinnamicacid 4.56 4-Phenylbutanoic acid 4.76 N,N-Diethylaniline 6.61 Perimidine6.35 2-Naphthoic acid 4.17 Pilocarpine 6.87 1,10-Phenanthroline 4.842-Benzylpyridine 5.13 Acridine 5.58 Phenanthridine 5.58 Morphine 8.21Codeine 8.21 Papaverine 6.40 Strychnine 8.26 Brucine 8.28

It will, of course, be appreciated that the present invention is notlimited to those acids listed above and the skilled person will bereadily able to select other acids (or conjugate bases) having a pK_(a)in the range of 4 to 9, or optionally 5 to 8.

Optionally, each B is independently selected from the group consistingof a nitrogen base and an oxyanion. Accordingly, each B may be anitrogen base. Alternatively, each B may be an oxyanion base.Alternatively, there may be a mixture of nitrogen and oxyanion bases inone dye salt. For example, the four BH⁺ molecules may consist of twomolecules of acetic acid and two pyridinium ions, or alternatively onemolecule of acetic and three imidazolium ions. The skilled person willbe readily able to conceive of a variety of mixed dye salts within theambit of the present invention.

By “nitrogen base” it is meant a base containing at least one nitrogenatom, which can be protonated. Optionally, the nitrogen base is a C₅₋₁₂heteroaryl base, such as imidazole or pyridine. Imidazole is aparticularly preferred base in the present invention.

By “oxyanion” it is meant a base containing at least one oxyanion, whichcan be protonated. Optionally, the oxyanion base is a carboxylate base.A carboxylate base is an organic molecule comprising at least onecarboxylate (CO₂ ⁻) moiety. Optionally, the carboxylate base is offormula R⁵C(O)O⁻, wherein R⁵ is selected from C₁₋₁₂ alkyl, C₅₋₁₂ aryl orC₅₋₁₂ arylalkyl. Examples of carboxylate bases include acetate, benzoateetc.

The groups represented by R¹ and R² may be used for modifying or“tuning” the wavelength of λ_(max) of the dye. Electron-donatingsubstituents (e.g. alkoxy) at the ortho positions can produce ared-shift in the dye. In one preferred embodiment of the presentinvention, R¹ and R² are both C₁₋₈ alkoxy groups, preferably butoxy.Butoxy substituents advantageously shift the λ_(max) towards longerwavelengths in the near infrared, which are preferable for detection bycommercially available lasers. In another preferred embodiment R¹ and R²are both hydrogen, which provides an expeditious synthesis of therequisite naphthalocyanines.

The central metal atom M has been found, surprisingly, to have a verysignificant impact on the light stability of the compounds of thepresent invention. Previously, it was believed that the nature of theorganic naphthalocyanine chromophore was primarily responsible for therate at which such compounds degrade. However, it has now been foundthat certain metal naphthalocyanines show unusually high light stabilitycompared to other metals. Specifically, gallium and coppernaphthalocyanines have been shown to exhibit very good light stability,making these compounds highly suitable for netpage and Hyperlabel™applications in which the IR dye may be exposed to office lighting orsunlight for a year or more. Gallium compounds are particularlypreferred since these have a more red-shifted λ_(max) compared tocopper. A more red-shifted λ_(max) is preferred, because colored cyandyes are less likely to interfere with the IR dye's response to thenetpage pen.

Typically A¹ is a hydroxyl group (—OH). Alternatively, A¹ may beselected or modified to impart specific properties onto the dyemolecule. A¹ may be selected to add axial steric bulk to the dyemolecule, thereby reducing cofacial interactions between adjacent dyemolecules.

Optionally, the axial ligand, when present, adopts a conformation (or isconfigured) such that it effectively “protects” or blocks a π-face ofthe dye molecule. An axial ligand, which can form an “umbrella” over theπ-system and reduce cofacial interactions between adjacent dye moleculesis particularly suitable for use in the present invention.

It has been recognized by the present inventors that IR-absorbing dyecompounds of the prior art absorb, at least to some extent, in thevisible region of the spectrum. Indeed, the vast majority ofIR-absorbing dye compounds known in the prior art are black or green orbrown hues of black in the solid state. This visible absorption isclearly undesirable in “invisible” IR inks, especially IR inks for usein netpage or Hyperlabel™ systems.

It has further been recognized by the present inventors that thepresence of visible bands in the absorption spectra of IR-absorbing dyecompounds, and particularly IR-absorbing metal-ligand complexes, is atleast in part due to cofacial interactions between adjacent molecules.

Typically, IR-absorbing compounds comprise a n-system which forms asubstantially planar moiety in at least part of the molecule. There is anatural tendency for planar π-systems in adjacent molecules to stack ontop of each other via cofacial π-interactions, known as π-π stacking.Hence, IR-absorbing compounds have a natural tendency to group togethervia cofacial π-interactions, producing relatively weakly bound dimers,trimers etc. Without wishing to be bound by theory, it is understood bythe present inventors that π-π stacking of IR-absorbing compoundscontributes significantly to the production of visible absorption bandsin their IR spectra, which would not otherwise be present in thecorresponding monomeric compounds. This visible absorption is understoodto be due to broadening of IR absorption bands when π-systems stack ontop of each other and π-orbitals interact, producing small changes intheir respective energy levels. Broadening of IR absorption bands isundesirable in two respects: firstly, it reduces the intensity ofabsorption in the IR region; secondly, the IR absorption band tends totail into the visible region, producing highly coloured compounds.

Furthermore, the formation of coloured dimers, trimers etc. via π-πinteractions occurs both in the solid state and in solution. However, itis a particular problem in the solid state, where there are no solventmolecules to disrupt the formation of extended π-stacked oligomers. IRdyes having acceptable solution characteristics may still be intenselycoloured solids when printed onto paper. The ideal “invisible” IR dyeshould remain invisible when the solvent has evaporated or wicked intothe paper.

Dendrimers, for example, are useful for exerting maximum stericrepulsion since they have a plurality of branched chains, such aspolymeric chains. However, it will be appreciated from the above thatany moiety or group that can interfere sufficiently with the cofacialπ-π interactions of adjacent dye molecules will be suitable forminimizing visible absorption.

Alternatively (or in addition), A¹ may be selected to add furtherhydrophilicity to the dye molecule to increase its water-dispersibility.

Generally, the naphthalocyanine dyes according to the present inventionare synthesized via a cascaded coupling of four 2,3-dicyanonapthalene(1) molecules, although they may also be prepared from the corresponding1-amino-3-iminoisoindolene (2).

The cascaded base-catalysed macrocyclisation may be facilitated by metaltemplating, or it may proceed in the absence of a metal. Ifmacrocylisation is performed in the absence of a templating metal, thena metal may be readily inserted into the resultant metal-freenapthalocyanine. Subsequent sulfonation and salt formation proceed bystandard procedures. Further synthetic details are provided below in theExamples.

The term “hydrocarbyl” is used herein to refer to monovalent groupsconsisting generally of carbon and hydrogen. Hydrocarbyl groups thusinclude alkyl, alkenyl and alkynyl groups (in both straight and branchedchain forms), carbocyclic groups (including polycycloalkyl groups suchas bicyclooctyl and adamantyl) and aryl groups, and combinations of theforegoing, such as alkylcycloalkyl, alkylpolycycloalkyl, alkylaryl,alkenylaryl, alkynylaryl, cycloalkylaryl and cycloalkenylaryl groups.Similarly, the term “hydrocarbylene” refers to divalent groupscorresponding to the monovalent hydrocarbyl groups described above.

Unless specifically stated otherwise, up to four —C—C— and/or —C—Hmoieties in the hydrocarbyl group may be optionally interrupted by oneor more moieties selected from —O—; —NR^(w)—; —S—; —C(O)—; C(O)O—;—C(O)NR^(w)—; —S(O)—; —SO₂—; —SO₂O—; —SO₂N^(w)—; where R^(w) is a groupselected from H, C₁₋₁₂ alkyl, C₆₋₁₂ aryl or C₆₋₁₂ arylalkyl.

Unless specifically stated otherwise, where the hydrocarbyl groupcontains one or more —C═C— moieties, up to four —C═C— moieties mayoptionally be replaced by —C═N—. Hence, the term “hydrocarbyl” mayinclude moieties such as heteroaryl, ether, thioether, carboxy,hydroxyl, alkoxy, amine, thiol, amide, ester, ketone, sulfoxide,sulfonate, sulfonamide etc.

Unless specifically stated otherwise, the hydrocarbyl group may compriseup to four substituents independently selected from halogen, cyano,nitro, a hydrophilic group as defined above (e.g. —SO₃H, —SO₃K, —CO₂Na,—NH₃ ⁺, —NMe₃ ⁺ etc.) or a polymeric group as defined above (e.g. apolymeric group derived from polyethylene glycol).

The term “aryl” is used herein to refer to an aromatic group, such asphenyl, naphthyl or triptycenyl. C₆₋₁₂ aryl, for example, refers to anaromatic group having from 6 to 12 carbon atoms, excluding anysubstituents. The term “arylene”, of course, refers to divalent groupscorresponding to the monovalent aryl groups described above. Anyreference to aryl implicitly includes arylene, where appropriate.

The term “heteroaryl” refers to an aryl group, where 1, 2, 3 or 4 carbonatoms are replaced by a heteroatom selected from N, O or S. Examples ofheteroaryl (or heteroaromatic) groups include pyridyl, benzimidazolyl,indazolyl, quinolinyl, isoquinolinyl, indolinyl, isoindolinyl, indolyl,isoindolyl, furanyl, thiophenyl, pyrrolyl, thiazolyl, imidazolyl,oxazolyl, isoxazolyl, pyrazolyl, isoxazolonyl, piperazinyl, pyrimidinyl,piperidinyl, morpholinyl, pyrrolidinyl, isothiazolyl, triazolyl,oxadiazolyl, thiadiazolyl, pyridyl, pyrimidinyl, benzopyrimidinyl,benzotriazole, quinoxalinyl, pyridazyl, coumarinyl etc. The term“heteroarylene”, of course, refers to divalent groups corresponding tothe monovalent heteroaryl groups described above. Any reference toheteroaryl implicitly includes heteroarylene, where appropriate.

Unless specifically stated otherwise, aryl, arylene, heteroaryl andheteroarylene groups may be optionally substituted with 1, 2, 3, 4 or 5of the substituents described below.

Where reference is made to optionally substituted groups (e.g. inconnection with bridged cyclic groups, aryl groups or heteroarylgroups), the optional substituent(s) are independently selected fromC₁₋₈ alkyl, C₁₋₈ alkoxy, —(OCH₂CH₂)_(d)OR^(d) (wherein d is an integerfrom 2 to 5000 and R^(d) is H, C₁₋₈ alkyl or C(O)C₁₋₈ alkyl), cyano,halogen, amino, hydroxyl, thiol, —SR^(v), —NR^(u)R^(v), nitro, phenyl,phenoxy, —CO₂R^(v), —C(O)R^(v), —OCOR^(v), —SO₂R^(v), —OSO₂R^(v),—SO₂OR^(v), —NHC(O)R^(v), —CONR^(u)R^(v), —CONR^(u)R^(v),—SO₂NR^(u)R^(v), wherein R^(u) and R^(v) are independently selected fromhydrogen, C₁₋₁₂ alkyl, phenyl or phenyl-C₁₋₈ alkyl (e.g. benzyl). Where,for example, a group contains more than one substituent, differentsubstituents can have different R^(u) or R^(v) groups. For example, anaphthyl group may be substituted with three substituents: —SO₂NHPh,—CO₂Me group and —NH₂.

The term “alkyl” is used herein to refer to alkyl groups in bothstraight and branched forms, The alkyl group may be interrupted with 1,2 or 3 heteroatoms selected from O, N or S. The alkyl group may also beinterrupted with 1, 2 or 3 double and/or triple bonds. However, the term“alkyl” usually refers to alkyl groups having no heteroatominterruptions or double or triple bond interruptions. Where “alkenyl”groups are specifically mentioned, this is not intended to be construedas a limitation on the definition of “alkyl” above.

The term “alkyl” also includes halogenoalkyl groups. A C₁₋₁₂ alkyl groupmay, for example, have up to 5 hydrogen atoms replaced by halogen atoms.For example, the group —OC(O)C₁₋₁₂ alkyl specifically includes—OC(O)CF₃.

Where reference is made to, for example, C₁₋₁₂ alkyl, it is meant thealkyl group may contain any number of carbon atoms between 1 and 12.Unless specifically stated otherwise, any reference to “alkyl” meansC₁₋₁₂ alkyl, preferably C₁₋₆ alkyl.

The term “alkyl” also includes cycloalkyl groups. As used herein, theterm “cycloalkyl” includes cycloalkyl, polycycloalkyl, and cycloalkenylgroups, as well as combinations of these with linear alkyl groups, suchas cycloalkylalkyl groups. The cycloalkyl group may be interrupted with1, 2 or 3 heteroatoms selected from O, N or S. However, the term“cycloalkyl” usually refers to cycloalkyl groups having no heteroatominterruptions. Examples of cycloalkyl groups include cyclopentyl,cyclohexyl, cyclohexenyl, cyclohexylmethyl and adamantyl groups.

The term “arylalkyl” refers to groups such as benzyl, phenylethyl andnaphthylmethyl.

The term “halogen” or “halo” is used herein to refer to any of fluorine,chlorine, bromine and iodine. Usually, however, halogen refers tochlorine or fluorine substituents.

Where reference is made to “a substituent comprising.” (e.g. “asubstituent comprising a hydrophilic group”, “a substituent comprisingan acid group (including salts thereof)”, “a substituent comprising apolymeric chain” etc.), the substituent in question may consist entirelyor partially of the group specified. For example, “a substituentcomprising an acid group (including salts thereof)” may be of formula—(CH₂)_(j)—SO₃K, wherein j is 0 or an integer from 1 to 6. Hence, inthis context, the term “substituent” may be, for example, an alkylgroup, which has a specified group attached. However, it will be readilyappreciated that the exact nature of the substituent is not crucial tothe desired functionality, provided that the specified group is present.

Chiral compounds described herein have not been givenstereo-descriptors. However, when compounds may exist in stereoisomericforms, then all possible stereoisomers and mixtures thereof are included(e.g. enantiomers, diastereomers and all combinations including racemicmixtures etc.).

Likewise, when compounds may exist in a number of regioisomeric forms,then all possible regioisomers and mixtures thereof are included.

For the avoidance of doubt, the term “a” (or “an”), in phrases such as“comprising a”, means “at least one” and not “one and only one”. Wherethe term “at least one” is specifically used, this should not beconstrued as having a limitation on the definition of “a”.

Throughout the specification, the term “comprising”, or variations suchas “comprise” or “comprises”, should be construed as including a statedelement, integer or step, but not excluding any other element, integeror step.

Inkjet Inks

The present invention also provides an inkjet ink. Preferably, theinkjet ink is a water-based inkjet ink.

Water-based inkjet ink compositions are well known in the literatureand, in addition to water, may comprise additives, such as co-solvents,biocides, sequestering agents, humectants, viscosity modifiers,penetrants, wetting agents, surfactants etc.

Co-solvents are typically water-soluble organic solvents. Suitablewater-soluble organic solvents include C₁₋₄ alkyl alcohols, such asethanol, methanol, butanol, propanol, and 2-propanol; glycol ethers,such as ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monobutyl ether, ethylene glycol monomethyl etheracetate, diethylene glycol monomethyl ether, diethylene glycol monoethylether, diethylene glycol mono-n-propyl ether, ethylene glycolmono-isopropyl ether, diethylene glycol mono-isopropyl ether, ethyleneglycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether,triethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butylether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol,propylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol mono-t-butyl ether, propylene glycol mono-n-propylether, propylene glycol mono-isopropyl ether, dipropylene glycolmonomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycolmono-n-propyl ether, dipropylene glycol mono-isopropyl ether, propyleneglycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether;formamide, acetamide, dimethyl sulfoxide, sorbitol, sorbitan, glycerolmonoacetate, glycerol diacetate, glycerol triacetate, and sulfolane; orcombinations thereof.

Other useful water-soluble organic solvents include polar solvents, suchas 2-pyrrolidone, N-methylpyrrolidone, ε-caprolactam, dimethylsulfoxide, sulfolane, morpholine, N-ethylmorpholine,1,3-dimethyl-2-imidazolidinone and combinations thereof.

The inkjet ink may contain a high-boiling water-soluble organic solventwhich can serve as a wetting agent or humectant for imparting waterretentivity and wetting properties to the ink composition. Such ahigh-boiling water-soluble organic solvent includes one having a boilingpoint of 180° C. or higher. Examples of the water-soluble organicsolvent having a boiling point of 180° C. or higher are ethylene glycol,propylene glycol, diethylene glycol, pentamethylene glycol, trimethyleneglycol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol,2-methyl-2,4-pentanediol, tripropylene glycol monomethyl ether,dipropylene glycol monoethyl glycol, dipropylene glycol monoethyl ether,dipropylene glycol monomethyl ether, dipropylene glycol, triethyleneglycol monomethyl ether, tetraethylene glycol, triethylene glycol,diethylene glycol monobutyl ether, diethylene glycol monoethyl ether,diethylene glycol monomethyl ether, tripropylene glycol, polyethyleneglycols having molecular weights of 2000 or lower, 1,3-propylene glycol,isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol,1,5-pentanediol, 1,6-hexanediol, glycerol, erythritol, pentaerythritoland combinations thereof.

The total water-soluble organic solvent content in the inkjet ink ispreferably about 5 to 50% by weight, more preferably 10 to 30% byweight, based on the total ink composition.

Other suitable wetting agents or humectants include saccharides(including monosaccharides, oligosaccharides and polysaccharides) andderivatives thereof (e.g. maltitol, sorbitol, xylitol, hyaluronic salts,aldonic acids, uronic acids etc.)

The inkjet ink may also contain a penetrant for accelerating penetrationof the aqueous ink into the recording medium. Suitable penetrantsinclude polyhydric alcohol alkyl ethers (glycol ethers) and/or1,2-alkyldiols. Examples of suitable polyhydric alcohol alkyl ethers areethylene glycol monomethyl ether, ethylene glycol monoethyl ether,ethylene glycol monobutyl ether, ethylene glycol monomethyl etheracetate, diethylene glycol monomethyl ether, diethylene glycol monoethylether, ethylene glycol mono-n-propyl ether, ethylene glycolmono-isopropyl ether, diethylene glycol mono-isopropyl ether, ethyleneglycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether,triethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butylether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol,propylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol mono-t-butyl ether, propylene glycol mono-n-propylether, propylene glycol mono-isopropyl ether, dipropylene glycolmonomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycolmono-n-propyl ether, dipropylene glycol mono-isopropyl ether, propyleneglycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether.Examples of suitable 1,2-alkyldiols are 1,2-pentanediol and1,2-hexanediol. The penetrant may also be selected from straight-chainhydrocarbon diols, such as 1,3-propanediol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol.Glycerol or urea may also be used as penetrants.

The amount of penetrant is preferably in the range of 1 to 20% byweight, more preferably 1 to 10% by weight, based on the total inkcomposition.

The inkjet ink may also contain a surface active agent, especially ananionic surface active agent and/or a nonionic surface active agent.Useful anionic surface active agents include sulfonic acid types, suchas alkanesulfonic acid salts, α-olefinsulfonic acid salts,alkylbenzenesulfonic acid salts, alkylnaphthalenesulfonic acids,acylmethyltaurines, and dialkylsulfosuccinic acids; alkylsulfuric estersalts, sulfated oils, sulfated olefins, polyoxyethylene alkyl ethersulfuric ester salts; carboxylic acid types, e.g., fatty acid salts andalkylsarcosine salts; and phosphoric acid ester types, such asalkylphosphoric ester salts, polyoxyethylene alkyl ether phosphoricester salts, and glycerophosphoric ester salts. Specific examples of theanionic surface active agents are sodium dodecylbenzenesulfonate, sodiumlaurate, and a polyoxyethylene alkyl ether sulfate ammonium salt.

Suitable nonionic surface active agents include ethylene oxide adducttypes, such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenylethers, polyoxyethylene alkyl esters, and polyoxyethylene alkylamides;polyol ester types, such as glycerol alkyl esters, sorbitan alkylesters, and sugar alkyl esters; polyether types, such as polyhydricalcohol alkyl ethers; and alkanolamide types, such as alkanolamine fattyacid amides. Specific examples of nonionic surface active agents areethers such as polyoxyethylene nonylphenyl ether, polyoxyethyleneoctylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylenealkylallyl ether, polyoxyethylene oleyl ether, polyoxyethylene laurylether, and polyoxyalkylene alkyl ethers (e.g. polyoxyethylene alkylethers); and esters, such as polyoxyethylene oleate, polyoxyethyleneoleate ester, polyoxyethylene distearate, sorbitan laurate, sorbitanmonostearate, sorbitan mono-oleate, sorbitan sesquioleate,polyoxyethylene mono-oleate, and polyoxyethylene stearate. Acetyleneglycol surface active agents, such as2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol or3,5-dimethyl-1-hexyn-3-ol, may also be used.

The inkjet ink may also include a biocide, such as benzoic acid,dichlorophene, hexachlorophene, sorbic acid, hydroxybenzoic esters,sodium dehydroacetate, 1,2-benthiazolin-3-one, 3,4-isothiazolin-3-one or4,4-dimethyloxazolidine.

The inkjet ink may also contain a sequestering agent, such asethylenediaminetetraacetic acid (EDTA).

The inkjet ink may also contain a singlet oxygen quencher. The presenceof singlet oxygen quencher(s) in the ink reduces the propensity for theIR-absorbing dye to degrade. The quencher consumes any singlet oxygengenerated in the vicinity of the dye molecules and, hence, minimizestheir degradation. An excess of singlet oxygen quencher is advantageousfor minimizing degradation of the dye and retaining its IR-absorbingproperties over time. Preferably, the singlet oxygen quencher isselected from ascorbic acid, 1,4-diazabicyclo-[2.2.2]octane (DABCO),azides (e.g. sodium azide), histidine or tryptophan.

Inkjet Printers

The present invention also provides an inkjet printer comprising aprinthead in fluid communication with at least one ink reservoir,wherein said ink reservoir comprises an inkjet ink as described above.

Inkjet printers, such as thermal bubble-jet and piezoelectric printers,are well known in the art and will form part of the skilled person'scommon general knowledge. The printer may be a high-speed inkjetprinter. The printer is preferably a pagewidth printer. Preferred inkjetprinters and printheads for use in the present invention are describedin the following patent applications, all of which are incorporatedherein by reference in their entirety.

Ser. No. 10/302,274 U.S. Pat. No. 6,692,108 U.S. Pat. No. 6,672,709 Ser.No. 10/303,348 U.S. Pat. No. 6,672,710

U.S. Pat. No. 6,669,334

Ser. No. 10/302,668 Ser. No. 10/302,577 U.S. Pat. No. 6,669,333 Ser. No.10/302,618 Ser. No. 10/302,617 Ser. No. 10/302,297

Printhead

A Memjet printer generally has two printhead integrated circuits thatare mounted adjacent each other to form a pagewidth printhead.Typically, the printhead ICs can vary in size from 2 inches to 8 inches,so several combinations can be used to produce, say, an A4 pagewidthprinthead. For example two printhead ICs of 7 and 3 inches, 2 and 4inches, or 5 and 5 inches could be used to create an A4 printhead (thenotation is 7:3). Similarly 6 and 4 (6:4) or 5 and 5 (5:5) combinationscan be used. An A3 printhead can be constructed from 8 and 6-inchprinthead integrated circuits, for example. For photographic printing,particularly in camera, smaller printheads can be used. It will also beappreciated that a single printhead integrated circuit, or more than twosuch circuits, can also be used to achieve the required printhead width.

A preferred printhead embodiment of the pinthead will now be describedwith reference to FIGS. 17 and 18. A printhead 420 takes the form of anelongate unit. As best shown in FIG. 18, the components of the printhead420 include a support member 421, a flexible PCB 422, an inkdistribution molding 423, an ink distribution plate 424, a MEMSprinthead comprising first and second printhead integrated circuits(ICs) 425 and 426, and busbars 427.

The support member 421 is can be formed from any suitable material, suchas metal or plastic, and can be extruded, molded or formed in any otherway. The support member 421 should be strong enough to hold the othercomponents in the appropriate alignment relative to each other whilststiffening and strengthening the printhead as a whole.

The flexible PCB extends the length of the printhead 420 and includesfirst and second electrical connectors 428 and 429. The electricalconnectors 428 and 429 correspond with flexible connectors (not shown).The electrical connectors include contact areas 450 and 460 that, inuse, are positioned in contact with corresponding output connectors froma SoPEC chip (not shown). Data from the SoPEC chip passes along theelectrical connectors 428 and 429, and is distributed to respective endsof the first and second printhead ICs 425 and 426.

As shown in FIG. 19, the ink distribution molding 423 includes aplurality of elongate conduits 430 that distribute fluids (ie, coloredinks, infrared ink and fixative) and pressurized air from the air pumpalong the length of the printhead 420 (FIG. 18). Sets of fluid apertures431 (FIG. 20) disposed along the length of the ink distribution molding423 distribute the fluids and air from the conduits 430 to the inkdistribution plate 424. The fluids and air are supplied via nozzles 440formed on a plug 441 (FIG. 21), which plugs into a corresponding socket(not shown) in the printer.

The distribution plate 424 is a multi-layer construction configured totake fluids provided locally from the fluid apertures 431 and distributethem through smaller distribution apertures 432 into the printhead ICs425 and 426 (as shown in FIG. 20).

The printhead ICs 425 and 426 are positioned end to end, and are held incontact with the distribution plate 424 so that ink from the smallerdistribution apertures 432 can be fed into corresponding apertures (notshown) in the printhead ICs 425 and 426.

The busbars 427 are relatively high-capacity conductors positioned toprovide drive current to the actuators of the printhead nozzles(described in detail below). As best shown in FIG. 20, the busbars 427are retained in position at one end by a socket 433, and at both ends bywrap-around wings 434 of the flexible PCB 422. The busbars also helphold the printhead ICs 425 in position.

As shown best in FIG. 18, when assembled, the flexible PCB 422 iseffectively wrapped around the other components, thereby holding them incontact with each other. Notwithstanding this binding effect, thesupport member 421 provides a major proportion of the required stiffnessand strength of the printhead 420 as a whole.

Two forms of printhead nozzles (“thermal bend actuator” and “bubbleforming heater element actuator”), suitable for use in the printheaddescribed above, will now be described.

Thermal Bend Actuator

In the thermal bend actuator, there is typically provided a nozzlearrangement having a nozzle chamber containing ink and a thermal bendactuator connected to a paddle positioned within the chamber. Thethermal actuator device is actuated so as to eject ink from the nozzlechamber. The preferred embodiment includes a particular thermal bendactuator which includes a series of tapered portions for providingconductive heating of a conductive trace. The actuator is connected tothe paddle via an arm received through a slotted wall of the nozzlechamber. The actuator arm has a mating shape so as to mate substantiallywith the surfaces of the slot in the nozzle chamber wall.

Turning initially to FIGS. 22( a)-(c), there is provided schematicillustrations of the basic operation of a nozzle arrangement of thisembodiment. A nozzle chamber 501 is provided filled with ink 502 bymeans of an ink inlet channel 503 which can be etched through a wafersubstrate on which the nozzle chamber 501 rests. The nozzle chamber 501further includes an ink ejection port 504 around which an ink meniscusforms.

Inside the nozzle chamber 501 is a paddle type device 507 which isinterconnected to an actuator 508 through a slot in the wall of thenozzle chamber 501. The actuator 508 includes a heater means e.g. 509located adjacent to an end portion of a post 510. The post 510 is fixedto a substrate.

When it is desired to eject a drop from the nozzle chamber 501, asillustrated in FIG. 22( b), the heater means 509 is heated so as toundergo thermal expansion. Preferably, the heater means 509 itself orthe other portions of the actuator 508 are built from materials having ahigh bend efficiency where the bend efficiency is defined as:

${{bend}{\mspace{11mu} \;}{efficiency}} = \frac{\begin{matrix}{{Young}^{\prime}s\mspace{14mu} {Modulus} \times} \\\left( {{Coefficient}\mspace{14mu} {of}\mspace{14mu} {thermal}\mspace{14mu} {Expansion}} \right)\end{matrix}}{{Density} \times {Specific}\mspace{14mu} {Heat}\mspace{14mu} {Capacity}}$

A suitable material for the heater elements is a copper nickel alloywhich can be formed so as to bend a glass material.

The heater means 509 is ideally located adjacent the end portion of thepost 510 such that the effects of activation are magnified at the paddleend 507 such that small thermal expansions near the post 510 result inlarge movements of the paddle end.

The heater means 509 and consequential paddle movement causes a generalincrease in pressure around the ink meniscus 505 which expands, asillustrated in FIG. 22( b), in a rapid manner. The heater current ispulsed and ink is ejected out of the port 504 in addition to flowing infrom the ink channel 503.

Subsequently, the paddle 507 is deactivated to again return to itsquiescent position. The deactivation causes a general reflow of the inkinto the nozzle chamber. The forward momentum of the ink outside thenozzle rim and the corresponding backflow results in a general neckingand breaking off of the drop 512 which proceeds to the print media. Thecollapsed meniscus 505 results in a general sucking of ink into thenozzle chamber 502 via the ink flow channel 503. In time, the nozzlechamber 501 is refilled such that the position in FIG. 22( a) is againreached and the nozzle chamber is subsequently ready for the ejection ofanother drop of ink.

FIG. 23 illustrates a side perspective view of the nozzle arrangement.FIG. 24 illustrates sectional view through an array of nozzlearrangement of FIG. 23. In these figures, the numbering of elementspreviously introduced has been retained.

Firstly, the actuator 508 includes a series of tapered actuator unitse.g. 515 which comprise an upper glass portion (amorphous silicondioxide) 516 formed on top of a titanium nitride layer 517.Alternatively a copper nickel alloy layer (hereinafter calledcupronickel) can be utilized which will have a higher bend efficiency.

The titanium nitride layer 517 is in a tapered form and, as such,resistive heating takes place near an end portion of the post 510.Adjacent titanium nitride/glass portions 515 are interconnected at ablock portion 519 which also provides a mechanical structural supportfor the actuator 508.

The heater means 509 ideally includes a plurality of the taperedactuator unit 515 which are elongate and spaced apart such that, uponheating, the bending force exhibited along the axis of the actuator 508is maximized. Slots are defined between adjacent tapered units 515 andallow for slight differential operation of each actuator 508 withrespect to adjacent actuators 508.

The block portion 519 is interconnected to an arm 520. The arm 520 is inturn connected to the paddle 507 inside the nozzle chamber 501 by meansof a slot e.g. 522 formed in the side of the nozzle chamber 501. Theslot 522 is designed generally to mate with the surfaces of the arm 520so as to minimize opportunities for the outflow of ink around the arm520. The ink is held generally within the nozzle chamber 501 via surfacetension effects around the slot 522.

When it is desired to actuate the arm 520, a conductive current ispassed through the titanium nitride layer 517 via vias within the blockportion 519 connecting to a lower CMOS layer 506 which provides thenecessary power and control circuitry for the nozzle arrangement. Theconductive current results in heating of the nitride layer 517 adjacentto the post 510 which results in a general upward bending of the arm 20and consequential ejection of ink out of the nozzle 504. The ejecteddrop is printed on a page in the usual manner for an inkjet printer aspreviously described.

An array of nozzle arrangements can be formed so as to create a singleprinthead. For example, in FIG. 24 there is illustrated a partlysectioned various array view which comprises multiple ink ejectionnozzle arrangements of FIG. 23 laid out in interleaved lines so as toform a printhead array. Of course, different types of arrays can beformulated including full color arrays etc.

The construction of the printhead system described can proceed utilizingstandard MEMS techniques through suitable modification of the steps asset out in U.S. Pat. No. 6,243,113 entitled “Image Creation Method andApparatus (IJ 41)” to the present applicant, the contents of which arefully incorporated by cross reference.

Bubble Forming Heater Element Actuator

With reference to FIG. 17, the unit cell 1001 of a bubble forming heaterelement actuator comprises a nozzle plate 1002 with nozzles 1003therein, the nozzles having nozzle rims 1004, and apertures 1005extending through the nozzle plate. The nozzle plate 1002 is plasmaetched from a silicon nitride structure which is deposited, by way ofchemical vapor deposition (CVD), over a sacrificial material which issubsequently etched.

The printhead also includes, with respect to each nozzle 1003, sidewalls 1006 on which the nozzle plate is supported, a chamber 1007defined by the walls and the nozzle plate 1002, a multi-layer substrate1008 and an inlet passage 1009 extending through the multi-layersubstrate to the far side (not shown) of the substrate. A looped,elongate heater element 1010 is suspended within the chamber 1007, sothat the element is in the form of a suspended beam. The printhead asshown is a microelectromechanical system (MEMS) structure, which isformed by a lithographic process.

When the printhead is in use, ink 1011 from a reservoir (not shown)enters the chamber 1007 via the inlet passage 1009, so that the chamberfills. Thereafter, the heater element 1010 is heated for somewhat lessthan 1 micro second, so that the heating is in the form of a thermalpulse. It will be appreciated that the heater element 1010 is in thermalcontact with the ink 1011 in the chamber 1007 so that when the elementis heated, this causes the generation of vapor bubbles in the ink.Accordingly, the ink 1011 constitutes a bubble forming liquid.

The bubble 1012, once generated, causes an increase in pressure withinthe chamber 1007, which in turn causes the ejection of a drop 1016 ofthe ink 1011 through the nozzle 1003. The rim 1004 assists in directingthe drop 1016 as it is ejected, so as to minimize the chance of a dropmisdirection.

The reason that there is only one nozzle 1003 and chamber 1007 per inletpassage 1009 is so that the pressure wave generated within the chamber,on heating of the element 1010 and forming of a bubble 1012, does noteffect adjacent chambers and their corresponding nozzles.

The increase in pressure within the chamber 1007 not only pushes ink1011 out through the nozzle 1003, but also pushes some ink back throughthe inlet passage 1009. However, the inlet passage 1009 is approximately200 to 300 microns in length, and is only approximately 16 microns indiameter. Hence there is a substantial viscous drag. As a result, thepredominant effect of the pressure rise in the chamber 1007 is to forceink out through the nozzle 1003 as an ejected drop 1016, rather thanback through the inlet passage 9.

As shown in FIG. 17, the ink drop 1016 is being ejected is shown duringits “necking phase” before the drop breaks off. At this stage, thebubble 1012 has already reached its maximum size and has then begun tocollapse towards the point of collapse 1017.

The collapsing of the bubble 1012 towards the point of collapse 1017causes some ink 1011 to be drawn from within the nozzle 1003 (from thesides 1018 of the drop), and some to be drawn from the inlet passage1009, towards the point of collapse. Most of the ink 1011 drawn in thismanner is drawn from the nozzle 1003, forming an annular neck 1019 atthe base of the drop 16 prior to its breaking off.

The drop 1016 requires a certain amount of momentum to overcome surfacetension forces, in order to break off. As ink 1011 is drawn from thenozzle 1003 by the collapse of the bubble 1012, the diameter of the neck1019 reduces thereby reducing the amount of total surface tensionholding the drop, so that the momentum of the drop as it is ejected outof the nozzle is sufficient to allow the drop to break off.

When the drop 1016 breaks off, cavitation forces are caused as reflectedby the arrows 1020, as the bubble 1012 collapses to the point ofcollapse 1017. It will be noted that there are no solid surfaces in thevicinity of the point of collapse 1017 on which the cavitation can havean effect.

Inkjet Cartridges

The present invention also provides an inkjet ink cartridge comprisingan inkjet ink as described above. Ink cartridges for inkjet printers arewell known in the art and are available in numerous forms. Preferably,the inkjet ink cartridges of the present invention are replaceable.Inkjet cartridges suitable for use in the present invention aredescribed in the following patent applications, all of which areincorporated herein by reference in their entirety.

U.S. Pat. No. 6,428,155, Ser. No. 10/171,987

In one preferred form, the ink cartridge comprises:

a housing defining a plurality of storage areas wherein at least one ofthe storage areas contains colorant for printing information that isvisible to the human eye and at least one of the other storage areascontains an inkjet ink as described above.

Preferably, each storage area is sized corresponding to the expectedlevels of use of its contents relative to the intended print coveragefor a number of printed pages.

There now follows a brief description of an ink cartridge according tothe present invention. FIG. 12 shows the complete assembly of thereplaceable ink cartridge 627. It has bladders or chambers for storingfixative 644, adhesive 630, and cyan 631, magenta 632, yellow 633, black634 and infrared 635 inks. The cartridge 627 also contains a micro airfilter 636 in a base molding 637. As shown in FIG. 9, the micro airfilter 636 interfaces with an air pump 638 inside the printer via a hose639. This provides filtered air to the printheads 705 to prevent ingressof micro particles into the Memjet™ printheads 705 which may clog thenozzles. By incorporating the air filter 636 within the cartridge 627,the operational life of the filter is effectively linked to the life ofthe cartridge. This ensures that the filter is replaced together withthe cartridge rather than relying on the user to clean or replace thefilter at the required intervals. Furthermore, the adhesive and infraredink are replenished together with the visible inks and air filterthereby reducing how frequently the printer operation is interruptedbecause of the depletion of a consumable material.

The cartridge 627 has a thin wall casing 640. The ink bladders 631 to635 and fixitive bladder 644 are suspended within the casing by a pin645 which hooks the cartridge together. The single glue bladder 630 isaccommodated in the base molding 637. This is a fully recyclable productwith a capacity for printing and gluing 3000 pages (1500 sheets).

Substrates

As mentioned above, the dyes of the present invention are especiallysuitable for use in Hyperlabel™ and netpage systems. Such systems aredescribed in more detail below and in the patent applications listedabove, all of which are incorporated herein by reference in theirentirety.

Hence, the present invention provides a substrate having an IR-absorbingdye as described above disposed thereon. Preferably, the substratecomprises an interface surface. Preferably, the dye is disposed in theform of coded data suitable for use in netpage and/or Hyperlabel™systems. For example, the coded data may be indicative of the identityof a product item. Preferably, the coded data is disposed over asubstantial portion of an interface surface of the substrate (e.g.greater than 20%, greater than 50% or greater than 90% of the surface).

Preferably, the substrate is IR reflective so that the dye disposedthereon may be detected by a sensing device. The substrate may becomprised of any suitable material such as plastics (e.g. polyolefins,polyesters, polyamides etc.), paper, metal or combinations thereof.

For netpage applications, the substrate is preferably a paper sheet. ForHyperlabel™ applications, the substrate is preferably a tag, a label, apackaging material or a surface of a product item. Typically, tags andlabels are comprised of plastics, paper or combinations thereof.

In accordance with Hyperlabel™ applications of the invention, thesubstrate may be an interactive product item adapted for interactionwith a user via a sensing device and a computer system, the interactiveproduct item comprising:

a product item having an identity;

an interface surface associated with the product item and havingdisposed thereon information relating to the product item and coded dataindicative of the identity of the product item, wherein said coded datacomprise an IR-absorbing dye as described above.

Netpage and Hyperlabel™

Netpage applications of this invention are described generally in thesixth and seventh aspects of the invention above. Hyperlabel™applications of this invention are described generally in the eighth andninth aspects of the invention above.

There now follows a detailed overview of netpage and Hyperlabel™. (Note:Memjet™ and Hyperlabel™ are trade marks of Silverbrook Research Pty Ltd,Australia). It will be appreciated that not every implementation willnecessarily embody all or even most of the specific details andextensions discussed below in relation to the basic system. However, thesystem is described in its most complete form to reduce the need forexternal reference when attempting to understand the context in whichthe preferred embodiments and aspects of the present invention operate.

In brief summary, the preferred form of the netpage system employs acomputer interface in the form of a mapped surface, that is, a physicalsurface which contains references to a map of the surface maintained ina computer system. The map references can be queried by an appropriatesensing device. Depending upon the specific implementation, the mapreferences may be encoded visibly or invisibly, and defined in such away that a local query on the mapped surface yields an unambiguous mapreference both within the map and among different maps. The computersystem can contain information about features on the mapped surface, andsuch information can be retrieved based on map references supplied by asensing device used with the mapped surface. The information thusretrieved can take the form of actions which are initiated by thecomputer system on behalf of the operator in response to the operator'sinteraction with the surface features.

In its preferred form, the netpage system relies on the production of,and human interaction with, netpages. These are pages of text, graphicsand images printed on ordinary paper, but which work like interactiveweb pages. Information is encoded on each page using ink which issubstantially invisible to the unaided human eye. The ink, however, andthereby the coded data, can be sensed by an optically imaging pen andtransmitted to the netpage system.

In the preferred form, active buttons and hyperlinks on each page can beclicked with the pen to request information from the network or tosignal preferences to a network server. In one embodiment, text writtenby hand on a netpage is automatically recognized and converted tocomputer text in the netpage system, allowing forms to be filled in. Inother embodiments, signatures recorded on a netpage are automaticallyverified, allowing e-commerce transactions to be securely authorized.

As illustrated in FIG. 1, a printed netpage 1 can represent aninteractive form which can be filled in by the user both physically, onthe printed page, and “electronically”, via communication between thepen and the netpage system. The example shows a “Request” formcontaining name and address fields and a submit button. The netpageconsists of graphic data 2 printed using visible ink, and coded data 3printed as a collection of tags 4 using invisible ink. The correspondingpage description 5, stored on the netpage network, describes theindividual elements of the netpage. In particular it describes the typeand spatial extent (zone) of each interactive element (i.e. text fieldor button in the example), to allow the netpage system to correctlyinterpret input via the netpage. The submit button 6, for example, has azone 7 which corresponds to the spatial extent of the correspondinggraphic 8.

As illustrated in FIG. 2, the netpage pen 101, a preferred form of whichis shown in FIGS. 6 and 7 and described in more detail below, works inconjunction with a personal computer, (PC), Web terminal 75, or anetpage printer 601. The netpage printer is an Internet-connectedprinting appliance for home, office or mobile use. The pen is wirelessand communicates securely with the netpage network via a short-rangeradio link 9. Short-range communication is relayed to the netpagenetwork by a local relay function which is either embedded in the PC,Web terminal or netpage printer, or is provided by a separate relaydevice 44. The relay function can also be provided by a mobile phone orother device which incorporates both short-range and longer-rangecommunications functions.

In an alternative embodiment, the netpage pen utilises a wiredconnection, such as a USB or other serial connection, to the PC, Webterminal, netpage printer or relay device.

The netpage printer 601, a preferred form of which is shown in FIGS. 9to 11 and described in more detail below, is able to deliver,periodically or on demand, personalized newspapers, magazines, catalogs,brochures and other publications, all printed at high quality asinteractive netpages. Unlike a personal computer, the netpage printer isan appliance which can be, for example, wall-mounted adjacent to an areawhere the morning news is first consumed, such as in a user's kitchen,near a breakfast table, or near the household's point of departure forthe day. It also comes in tabletop, desktop, portable and miniatureversions.

Netpages printed at their point of consumption combine the ease-of-useof paper with the timeliness and interactivity of an interactive medium.

As shown in FIG. 2, the netpage pen 101 interacts with the coded data ona printed netpage 1 (or product item 201) and communicates theinteraction via a short-range radio link 9 to a relay. The relay sendsthe interaction to the relevant netpage page server 10 forinterpretation. In appropriate circumstances, the page server sends acorresponding message to application computer software running on anetpage application server 13. The application server may in turn send aresponse which is printed on the originating printer.

In an alternative embodiment, the PC, Web terminal, netpage printer orrelay device may communicate directly with local or remote applicationsoftware, including a local or remote Web server. Relatedly, output isnot limited to being printed by the netpage printer. It can also bedisplayed on the PC or Web terminal, and further interaction can bescreen-based rather than paper-based, or a mixture of the two.

The netpage system is made considerably more convenient in the preferredembodiment by being used in conjunction with high-speedmicroelectromechanical system (MEMS) based inkjet (Memjet™) printers. Inthe preferred form of this technology, relatively high-speed andhigh-quality printing is made more affordable to consumers. In itspreferred form, a netpage publication has the physical characteristicsof a traditional newsmagazine, such as a set of letter-size glossy pagesprinted in full color on both sides, bound together for easy navigationand comfortable handling.

The netpage printer exploits the growing availability of broadbandInternet access. Cable service is available to 95% of households in theUnited States, and cable modem service offering broadband Internetaccess is already available to 20% of these. The netpage printer canalso operate with slower connections, but with longer delivery times andlower image quality. Indeed, the netpage system can be enabled usingexisting consumer inkjet and laser printers, although the system willoperate more slowly and will therefore be less acceptable from aconsumer's point of view. In other embodiments, the netpage system ishosted on a private intranet. In still other embodiments, the netpagesystem is hosted on a single computer or computer-enabled device, suchas a printer.

Netpage publication servers 14 on the netpage network are configured todeliver print-quality publications to netpage printers. Periodicalpublications are delivered automatically to subscribing netpage printersvia pointcasting and multicasting Internet protocols. Personalizedpublications are filtered and formatted according to individual userprofiles.

A netpage printer can be configured to support any number of pens, and apen can work with any number of netpage printers. In the preferredimplementation, each netpage pen has a unique identifier. A householdmay have a collection of colored netpage pens, one assigned to eachmember of the family. This allows each user to maintain a distinctprofile with respect to a netpage publication server or applicationserver.

A netpage pen can also be registered with a netpage registration server11 and linked to one or more payment card accounts. This allowse-commerce payments to be securely authorized using the netpage pen. Thenetpage registration server compares the signature captured by thenetpage pen with a previously registered signature, allowing it toauthenticate the user's identity to an e-commerce server. Otherbiometrics can also be used to verify identity. A version of the netpagepen includes fingerprint scanning, verified in a similar way by thenetpage registration server.

Although a netpage printer may deliver periodicals such as the morningnewspaper without user intervention, it can be configured never todeliver unsolicited junk mail. In its preferred form, it only deliversperiodicals from subscribed or otherwise authorized sources. In thisrespect, the netpage printer is unlike a fax machine or e-mail accountwhich is visible to any junk mailer who knows the telephone number oremail address.

1 Netpage System Architecture

Each object model in the system is described using a Unified ModelingLanguage (UML) class diagram. A class diagram consists of a set ofobject classes connected by relationships, and two kinds ofrelationships are of interest here: associations and generalizations. Anassociation represents some kind of relationship between objects, i.e.between instances of classes. A generalization relates actual classes,and can be understood in the following way: if a class is thought of asthe set of all objects of that class, and class A is a generalization ofclass B, then B is simply a subset of A. The UML does not directlysupport second-order modelling—i.e. classes of classes.

Each class is drawn as a rectangle labelled with the name of the class.It contains a list of the attributes of the class, separated from thename by a horizontal line, and a list of the operations of the class,separated from the attribute list by a horizontal line. In the classdiagrams which follow, however, operations are never modelled.

An association is drawn as a line joining two classes, optionallylabelled at either end with the multiplicity of the association. Thedefault multiplicity is one. An asterisk (*) indicates a multiplicity of“many”, i.e. zero or more. Each association is optionally labelled withits name, and is also optionally labelled at either end with the role ofthe corresponding class. An open diamond indicates an aggregationassociation (“is-part-of”), and is drawn at the aggregator end of theassociation line.

A generalization relationship (“is-a”) is drawn as a solid line joiningtwo classes, with an arrow (in the form of an open triangle) at thegeneralization end.

When a class diagram is broken up into multiple diagrams, any classwhich is duplicated is shown with a dashed outline in all but the maindiagram which defines it. It is shown with attributes only where it isdefined.

1.1 Netpages

Netpages are the foundation on which a netpage network is built. Theyprovide a paper-based user interface to published information andinteractive services.

A netpage consists of a printed page (or other surface region) invisiblytagged with references to an online description of the page. The onlinepage description is maintained persistently by a netpage page server.The page description describes the visible layout and content of thepage, including text, graphics and images. It also describes the inputelements on the page, including buttons, hyperlinks, and input fields. Anetpage allows markings made with a netpage pen on its surface to besimultaneously captured and processed by the netpage system.

Multiple netpages can share the same page description. However, to allowinput through otherwise identical pages to be distinguished, eachnetpage is assigned a unique page identifier. This page ID hassufficient precision to distinguish between a very large number ofnetpages.

Each reference to the page description is encoded in a printed tag. Thetag identifies the unique page on which it appears, and therebyindirectly identifies the page description. The tag also identifies itsown position on the page. Characteristics of the tags are described inmore detail below.

Tags are printed in infrared-absorptive ink on any substrate which isinfrared-reflective, such as ordinary paper. Near-infrared wavelengthsare invisible to the human eye but are easily sensed by a solid-stateimage sensor with an appropriate filter.

A tag is sensed by an area image sensor in the netpage pen, and the tagdata is transmitted to the netpage system via the nearest netpageprinter. The pen is wireless and communicates with the netpage printervia a short-range radio link. Tags are sufficiently small and denselyarranged that the pen can reliably image at least one tag even on asingle click on the page. It is important that the pen recognize thepage ID and position on every interaction with the page, since theinteraction is stateless. Tags are error-correctably encoded to makethem partially tolerant to surface damage.

The netpage page server maintains a unique page instance for eachprinted netpage, allowing it to maintain a distinct set of user-suppliedvalues for input fields in the page description for each printednetpage.

The relationship between the page description, the page instance, andthe printed netpage is shown in FIG. 4. The printed netpage may be partof a printed netpage document 45. The page instance is associated withboth the netpage printer which printed it and, if known, the netpageuser who requested it.

As shown in FIG. 4, one or more netpages may also be associated with aphysical object such as a product item, for example when printed ontothe product item's label, packaging, or actual surface.

1.2 Netpage Tags 1.2.1 Tag Data Content

In a preferred form, each tag identifies the region in which it appears,and the location of that tag within the region. A tag may also containflags which relate to the region as a whole or to the tag. One or moreflag bits may, for example, signal a tag sensing device to providefeedback indicative of a function associated with the immediate area ofthe tag, without the sensing device having to refer to a description ofthe region. A netpage pen may, for example, illuminate an “active area”LED when in the zone of a hyperlink.

As will be more clearly explained below, in a preferred embodiment, eachtag contains an easily recognized invariant structure which aids initialdetection, and which assists in minimizing the effect of any warpinduced by the surface or by the sensing process. The tags preferablytile the entire page, and are sufficiently small and densely arrangedthat the pen can reliably image at least one tag even on a single clickon the page. It is important that the pen recognize the page ID andposition on every interaction with the page, since the interaction isstateless.

In a preferred embodiment, the region to which a tag refers coincideswith an entire page, and the region ID encoded in the tag is thereforesynonymous with the page ID of the page on which the tag appears. Inother embodiments, the region to which a tag refers can be an arbitrarysubregion of a page or other surface. For example, it can coincide withthe zone of an interactive element, in which case the region ID candirectly identify the interactive element.

In the preferred form, each tag contains 120 bits of information. Theregion ID is typically allocated up to 100 bits, the tag ID at least 16bits, and the remaining bits are allocated to flags etc. Assuming a tagdensity of 64 per square inch, a 16-bit tag ID supports a region size ofup to 1024 square inches. Larger regions can be mapped continuouslywithout increasing the tag ID precision simply by using abutting regionsand maps. The 100-bit region ID allows 2¹⁰⁰ (˜10³⁰ or a million trilliontrillion) different regions to be uniquely identified.

1.2.2 Tag Data Encoding

In one embodiment, the 120 bits of tag data are redundantly encodedusing a (15, 5) Reed-Solomon code. This yields 360 encoded bitsconsisting of 6 codewords of 15 4-bit symbols each. The (15, 5) codeallows up to 5 symbol errors to be corrected per codeword, i.e. it istolerant of a symbol error rate of up to 33% per codeword.

Each 4-bit symbol is represented in a spatially coherent way in the tag,and the symbols of the six codewords are interleaved spatially withinthe tag. This ensures that a burst error (an error affecting multiplespatially adjacent bits) damages a minimum number of symbols overall anda minimum number of symbols in any one codeword, thus maximising thelikelihood that the burst error can be fully corrected.

Any suitable error-correcting code can be used in place of a (15, 5)Reed-Solomon code, for example: a Reed-Solomon code with more or lessredundancy, with the same or different symbol and codeword sizes;another block code; or a different kind of code, such as a convolutionalcode (see, for example, Stephen B. Wicker, Error Control Systems forDigital Communication and Storage, Prentice-Hall 1995, the contents ofwhich a herein incorporated by reference thereto).

In order to support “single-click” interaction with a tagged region viaa sensing device, the sensing device must be able to see at least oneentire tag in its field of view no matter where in the region or at whatorientation it is positioned. The required diameter of the field of viewof the sensing device is therefore a function of the size and spacing ofthe tags.

1.2.3 Tag Structure

FIG. 5 a shows a tag 4, in the form of tag 726 with four perspectivetargets 17. The tag 726 represents sixty 4-bit Reed-Solomon symbols 747,for a total of 240 bits. The tag represents each “one” bit by thepresence of a mark 748, referred to as a macrodot, and each “zero” bitby the absence of the corresponding macrodot. FIG. 5 c shows a squaretiling 728 of nine tags, containing all “one” bits for illustrativepurposes. It will be noted that the perspective targets are designed tobe shared between adjacent tags. FIG. 5 d shows a square tiling of 16tags and a corresponding minimum field of view 193, which spans thediagonals of two tags.

Using a (15, 7) Reed-Solomon code, 112 bits of tag data are redundantlyencoded to produce 240 encoded bits. The four codewords are interleavedspatially within the tag to maximize resilience to burst errors.Assuming a 16-bit tag ID as before, this allows a region ID of up to 92bits.

The data-bearing macrodots 748 of the tag are designed to not overlaptheir neighbors, so that groups of tags cannot produce structures thatresemble targets. This also saves ink. The perspective targets allowdetection of the tag, so further targets are not required.

Although the tag may contain an orientation feature to allowdisambiguation of the four possible orientations of the tag relative tothe sensor, the present invention is concerned with embeddingorientation data in the tag data. For example, the four codewords can bearranged so that each tag orientation (in a rotational sense) containsone codeword placed at that orientation, as shown in FIG. 5 a, whereeach symbol is labelled with the number of its codeword (1-4) and theposition of the symbol within the codeword (A-O). Tag decoding thenconsists of decoding one codeword at each rotational orientation. Eachcodeword can either contain a single bit indicating whether it is thefirst codeword, or two bits indicating which codeword it is. The latterapproach has the advantage that if, say, the data content of only onecodeword is required, then at most two codewords need to be decoded toobtain the desired data. This may be the case if the region ID is notexpected to change within a stroke and is thus only decoded at the startof a stroke. Within a stroke only the codeword containing the tag ID isthen desired. Furthermore, since the rotation of the sensing devicechanges slowly and predictably within a stroke, only one codewordtypically needs to be decoded per frame.

It is possible to dispense with perspective targets altogether andinstead rely on the data representation being self-registering. In thiscase each bit value (or multi-bit value) is typically represented by anexplicit glyph, i.e. no bit value is represented by the absence of aglyph. This ensures that the data grid is well-populated, and thusallows the grid to be reliably identified and its perspective distortiondetected and subsequently corrected during data sampling. To allow tagboundaries to be detected, each tag data must contain a marker pattern,and these must be redundantly encoded to allow reliable detection. Theoverhead of such marker patterns is similar to the overhead of explicitperspective targets. Various such schemes are described in the presentapplicants' co-pending PCT application PCT/AU01/01274 filed 11 Oct.2001.

The arrangement 728 of FIG. 5 c shows that the square tag 726 can beused to fully tile or tesselate, i.e. without gaps or overlap, a planeof arbitrary size.

Although in preferred embodiments the tagging schemes described hereinencode a single data bit using the presence or absence of a singleundifferentiated macrodot, they can also use sets of differentiatedglyphs to represent single-bit or multi-bit values, such as the sets ofglyphs illustrated in the present applicants' co-pending PCT applicationPCT/AU01/01274 filed 11 Oct. 2001.

1.3 The Netpage Network

In a preferred embodiment, a netpage network consists of a distributedset of netpage page servers 10, netpage registration servers 11, netpageID servers 12, netpage application servers 13, netpage publicationservers 14, Web terminals 75, netpage printers 601, and relay devices 44connected via a network 19 such as the Internet, as shown in FIG. 3.

The netpage registration server 11 is a server which recordsrelationships between users, pens, printers, applications andpublications, and thereby authorizes various network activities. Itauthenticates users and acts as a signing proxy on behalf ofauthenticated users in application transactions. It also provideshandwriting recognition services. As described above, a netpage pageserver 10 maintains persistent information about page descriptions andpage instances. The netpage network includes any number of page servers,each handling a subset of page instances. Since a page server alsomaintains user input values for each page instance, clients such asnetpage printers send netpage input directly to the appropriate pageserver. The page server interprets any such input relative to thedescription of the corresponding page.

A netpage ID server 12 allocates document IDs 51 on demand, and providesload-balancing of page servers via its ID allocation scheme.

A netpage printer uses the Internet Distributed Name System (DNS), orsimilar, to resolve a netpage page ID 50 into the network address of thenetpage page server handling the corresponding page instance.

A netpage application server 13 is a server which hosts interactivenetpage applications. A netpage publication server 14 is an applicationserver which publishes netpage documents to netpage printers.

Netpage servers can be hosted on a variety of network server platformsfrom manufacturers such as IBM, Hewlett-Packard, and Sun. Multiplenetpage servers can run con-currently on a single host, and a singleserver can be distributed over a number of hosts. Some or all of thefunctionality provided by netpage servers, and in particular thefunctionality provided by the ID server and the page server, can also beprovided directly in a netpage appliance such as a netpage printer, in acomputer workstation, or on a local network.

1.4 The Netpage Printer

The netpage printer 601 is an appliance which is registered with thenetpage system and prints netpage documents on demand and viasubscription. Each printer has a unique printer ID 62, and is connectedto the netpage network via a network such as the Internet, ideally via abroadband connection.

Apart from identity and security settings in non-volatile memory, thenetpage printer contains no persistent storage. As far as a user isconcerned, “the network is the computer”. Netpages functioninteractively across space and time with the help of the distributednetpage page servers 10, independently of particular netpage printers.

The netpage printer receives subscribed netpage documents from netpagepublication servers 14. Each document is distributed in two parts: thepage layouts, and the actual text and image objects which populate thepages. Because of personalization, page layouts are typically specificto a particular subscriber and so are pointcast to the subscriber'sprinter via the appropriate page server. Text and image objects, on theother hand, are typically shared with other subscribers, and so aremulticast to all subscribers' printers and the appropriate page servers.

The netpage publication server optimizes the segmentation of documentcontent into pointcasts and multicasts. After receiving the pointcast ofa document's page layouts, the printer knows which multicasts, if any,to listen to.

Once the printer has received the complete page layouts and objects thatdefine the document to be printed, it can print the document.

The printer rasterizes and prints odd and even pages simultaneously onboth sides of the sheet. It contains duplexed print engine controllers760 and print engines utilizing Memjet™ printheads 350 for this purpose.

The printing process consists of two decoupled stages: rasterization ofpage descriptions, and expansion and printing of page images. The rasterimage processor (RIP) consists of one or more standard DSPs 757 runningin parallel. The duplexed print engine controllers consist of customprocessors which expand, dither and print page images in real time,synchronized with the operation of the printheads in the print engines.

Printers not enabled for IR printing have the option to print tags usingIR-absorptive black ink, although this restricts tags to otherwise emptyareas of the page. Although such pages have more limited functionalitythan IR-printed pages, they are still classed as netpages.

A normal netpage printer prints netpages on sheets of paper. Morespecialised netpage printers may print onto more specialised surfaces,such as globes. Each printer supports at least one surface type, andsupports at least one tag tiling scheme, and hence tag map, for eachsurface type. The tag map 811 which describes the tag tiling schemeactually used to print a document becomes associated with that documentso that the document's tags can be correctly interpreted.

FIG. 2 shows the netpage printer class diagram, reflectingprinter-related information maintained by a registration server 11 onthe netpage network.

1.5 The Netpage Pen

The active sensing device of the netpage system is typically a pen 101,which, using its embedded controller 134, is able to capture and decodeIR position tags from a page via an image sensor. The image sensor is asolid-state device provided with an appropriate filter to permit sensingat only near-infrared wavelengths. As described in more detail below,the system is able to sense when the nib is in contact with the surface,and the pen is able to sense tags at a sufficient rate to capture humanhandwriting (i.e. at 200 dpi or greater and 100 Hz or faster).Information captured by the pen is encrypted and wirelessly transmittedto the printer (or base station), the printer or base stationinterpreting the data with respect to the (known) page structure.

The preferred embodiment of the netpage pen operates both as a normalmarking ink pen and as a non-marking stylus. The marking aspect,however, is not necessary for using the netpage system as a browsingsystem, such as when it is used as an Internet interface. Each netpagepen is registered with the netpage system and has a unique pen ID 61.FIG. 14 shows the netpage pen class diagram, reflecting pen-relatedinformation maintained by a registration server 11 on the netpagenetwork.

When either nib is in contact with a netpage, the pen determines itsposition and orientation relative to the page. The nib is attached to aforce sensor, and the force on the nib is interpreted relative to athreshold to indicate whether the pen is “up” or “down”. This allows ainteractive element on the page to be ‘clicked’ by pressing with the pennib, in order to request, say, information from a network. Furthermore,the force is captured as a continuous value to allow, say, the fulldynamics of a signature to be verified.

The pen determines the position and orientation of its nib on thenetpage by imaging, in the infrared spectrum, an area 193 of the page inthe vicinity of the nib. It decodes the nearest tag and computes theposition of the nib relative to the tag from the observed perspectivedistortion on the imaged tag and the known geometry of the pen optics.Although the position resolution of the tag may be low, because the tagdensity on the page is inversely proportional to the tag size, theadjusted position resolution is quite high, exceeding the minimumresolution required for accurate handwriting recognition.

Pen actions relative to a netpage are captured as a series of strokes. Astroke consists of a sequence of time-stamped pen positions on the page,initiated by a pen-down event and completed by the subsequent pen-upevent. A stroke is also tagged with the page ID 50 of the netpagewhenever the page ID changes, which, under normal circumstances, is atthe commencement of the stroke.

Each netpage pen has a current selection 826 associated with it,allowing the user to perform copy and paste operations etc. Theselection is timestamped to allow the system to discard it after adefined time period. The current selection describes a region of a pageinstance. It consists of the most recent digital ink stroke capturedthrough the pen relative to the background area of the page. It isinterpreted in an application-specific manner once it is submitted to anapplication via a selection hyperlink activation.

Each pen has a current nib 824. This is the nib last notified by the pento the system. In the case of the default netpage pen described above,either the marking black ink nib or the non-marking stylus nib iscurrent. Each pen also has a current nib style 825. This is the nibstyle last associated with the pen by an application, e.g. in responseto the user selecting a color from a palette. The default nib style isthe nib style associated with the current nib. Strokes captured througha pen are tagged with the current nib style. When the strokes aresubsequently reproduced, they are reproduced in the nib style with whichthey are tagged.

Whenever the pen is within range of a printer with which it cancommunicate, the pen slowly flashes its “online” LED. When the pen failsto decode a stroke relative to the page, it momentarily activates its“error” LED. When the pen succeeds in decoding a stroke relative to thepage, it momentarily activates its “ok” LED.

A sequence of captured strokes is referred to as digital ink. Digitalink forms the basis for the digital exchange of drawings andhandwriting, for online recognition of handwriting, and for onlineverification of signatures.

The pen is wireless and transmits digital ink to the netpage printer viaa short-range radio link. The transmitted digital ink is encrypted forprivacy and security and packetized for efficient transmission, but isalways flushed on a pen-up event to ensure timely handling in theprinter.

When the pen is out-of-range of a printer it buffers digital ink ininternal memory, which has a capacity of over ten minutes of continuoushandwriting. When the pen is once again within range of a printer, ittransfers any buffered digital ink.

A pen can be registered with any number of printers, but because allstate data resides in netpages both on paper and on the network, it islargely immaterial which printer a pen is communicating with at anyparticular time.

A preferred embodiment of the pen is described in greater detail below,with reference to FIGS. 6 to 8.

1.6 Netpage Interaction

The netpage printer 601 receives data relating to a stroke from the pen101 when the pen is used to interact with a netpage 1. The coded data 3of the tags 4 is read by the pen when it is used to execute a movement,such as a stroke. The data allows the identity of the particular pageand associated interactive element to be determined and an indication ofthe relative positioning of the pen relative to the page to be obtained.The indicating data is transmitted to the printer, where it resolves,via the DNS, the page ID 50 of the stroke into the network address ofthe netpage page server 10 which maintains the corresponding pageinstance 830. It then transmits the stroke to the page server. If thepage was recently identified in an earlier stroke, then the printer mayalready have the address of the relevant page server in its cache. Eachnetpage consists of a compact page layout maintained persistently by anetpage page server (see below). The page layout refers to objects suchas images, fonts and pieces of text, typically stored elsewhere on thenetpage network.

When the page server receives the stroke from the pen, it retrieves thepage description to which the stroke applies, and determines whichelement of the page description the stroke intersects. It is then ableto interpret the stroke in the context of the type of the relevantelement.

A “click” is a stroke where the distance and time between the pen downposition and the subsequent pen up position are both less than somesmall maximum. An object which is activated by a click typicallyrequires a click to be activated, and accordingly, a longer stroke isignored. The failure of a pen action, such as a “sloppy” click, toregister is indicated by the lack of response from the pen's “ok” LED.

There are two kinds of input elements in a netpage page description:hyperlinks and form fields. Input through a form field can also triggerthe activation of an associated hyperlink.

2. Netpage Pen Description 2.1 Pen Mechanics

Referring to FIGS. 6 and 7, the pen, generally designated by referencenumeral 101, includes a housing 102 in the form of a plastics mouldinghaving walls 103 defining an interior space 104 for mounting the pencomponents. The pen top 105 is in operation rotatably mounted at one end106 of the housing 102. A semi-transparent cover 107 is secured to theopposite end 108 of the housing 102. The cover 107 is also of mouldedplastics, and is formed from semi-transparent material in order toenable the user to view the status of the LED mounted within the housing102. The cover 107 includes a main part 109 which substantiallysurrounds the end 108 of the housing 102 and a projecting portion 110which projects back from the main part 109 and fits within acorresponding slot 111 formed in the walls 103 of the housing 102. Aradio antenna 112 is mounted behind the projecting portion 110, withinthe housing 102. Screw threads 113 surrounding an aperture 113A on thecover 107 are arranged to receive a metal end piece 114, includingcorresponding screw threads 115. The metal end piece 114 is removable toenable ink cartridge replacement.

Also mounted within the cover 107 is a tri-color status LED 116 on aflex PCB 117. The antenna 112 is also mounted on the flex PCB 117. Thestatus LED 116 is mounted at the top of the pen 101 for good all-aroundvisibility.

The pen can operate both as a normal marking ink pen and as anon-marking stylus. An ink pen cartridge 118 with nib 119 and a stylus120 with stylus nib 121 are mounted side by side within the housing 102.Either the ink cartridge nib 119 or the stylus nib 121 can be broughtforward through open end 122 of the metal end piece 114, by rotation ofthe pen top 105. Respective slider blocks 123 and 124 are mounted to theink cartridge 118 and stylus 120, respectively. A rotatable cam barrel125 is secured to the pen top 105 in operation and arranged to rotatetherewith. The cam barrel 125 includes a cam 126 in the form of a slotwithin the walls 181 of the cam barrel. Cam followers 127 and 128projecting from slider blocks 123 and 124 fit within the cam slot 126.On rotation of the cam barrel 125, the slider blocks 123 or 124 moverelative to each other to project either the pen nib 119 or stylus nib121 out through the hole 122 in the metal end piece 114. The pen 101 hasthree states of operation. By turning the top 105 through 90° steps, thethree states are:

-   -   stylus 120 nib 121 out    -   ink cartridge 118 nib 119 out, and    -   neither ink cartridge 118 nib 119 out nor stylus 120 nib 121 out

A second flex PCB 129, is mounted on an electronics chassis 130 whichsits within the housing 102. The second flex PCB 129 mounts an infraredLED 131 for providing infrared radiation for projection onto thesurface. An image sensor 132 is provided mounted on the second flex PCB129 for receiving reflected radiation from the surface. The second flexPCB 129 also mounts a radio frequency chip 133, which includes an RFtransmitter and RF receiver, and a controller chip 134 for controllingoperation of the pen 101. An optics block 135 (formed from moulded clearplastics) sits within the cover 107 and projects an infrared beam ontothe surface and receives images onto the image sensor 132. Power supplywires 136 connect the components on the second flex PCB 129 to batterycontacts 137 which are mounted within the cam barrel 125. A terminal 138connects to the battery contacts 137 and the cam barrel 125. A threevolt rechargeable battery 139 sits within the cam barrel 125 in contactwith the battery contacts. An induction charging coil 140 is mountedabout the second flex PCB 129 to enable recharging of the battery 139via induction. The second flex PCB 129 also mounts an infrared LED 143and infrared photodiode 144 for detecting displacement in the cam barrel125 when either the stylus 120 or the ink cartridge 118 is used forwriting, in order to enable a determination of the force being appliedto the surface by the pen nib 119 or stylus nib 121. The IR photodiode144 detects light from the IR LED 143 via reflectors (not shown) mountedon the slider blocks 123 and 124.

Rubber grip pads 141 and 142 are provided towards the end 108 of thehousing 102 to assist gripping the pen 101, and top 105 also includes aclip 142 for clipping the pen 101 to a pocket.

3.2 Pen Controller

The pen 101 is arranged to determine the position of its nib (stylus nib121 or ink cartridge nib 119) by imaging, in the infrared spectrum, anarea of the surface in the vicinity of the nib. It records the locationdata from the nearest location tag, and is arranged to calculate thedistance of the nib 121 or 119 from the location tab utilising optics135 and controller chip 134. The controller chip 134 calculates theorientation of the pen and the nib-to-tag distance from the perspectivedistortion observed on the imaged tag.

Utilising the RF chip 133 and antenna 112 the pen 101 can transmit thedigital ink data (which is encrypted for security and packaged forefficient transmission) to the computing system.

When the pen is in range of a receiver, the digital ink data istransmitted as it is formed. When the pen 101 moves out of range,digital ink data is buffered within the pen 101 (the pen 101 circuitryincludes a buffer arranged to store digital ink data for approximately12 minutes of the pen motion on the surface) and can be transmittedlater.

The controller chip 134 is mounted on the second flex PCB 129 in the pen101. FIG. 8 is a block diagram illustrating in more detail thearchitecture of the controller chip 134. FIG. 8 also showsrepresentations of the RF chip 133, the image sensor 132, the tri-colorstatus LED 116, the IR illumination LED 131, the IR force sensor LED143, and the force sensor photodiode 144.

The pen controller chip 134 includes a controlling processor 145. Bus146 enables the exchange of data between components of the controllerchip 134. Flash memory 147 and a 512 KB DRAM 148 are also included. Ananalog-to-digital converter 149 is arranged to convert the analog signalfrom the force sensor photodiode 144 to a digital signal.

An image sensor interface 152 interfaces with the image sensor 132. Atransceiver controller 153 and base band circuit 154 are also includedto interface with the RF chip 133 which includes an RF circuit 155 andRF resonators and inductors 156 connected to the antenna 112.

The controlling processor 145 captures and decodes location data fromtags from the surface via the image sensor 132, monitors the forcesensor photodiode 144, controls the LEDs 116, 131 and 143, and handlesshort-range radio communication via the radio transceiver 153. It is amedium-performance (−40 MHz) general-purpose RISC processor.

The processor 145, digital transceiver components (transceivercontroller 153 and baseband circuit 154), image sensor interface 152,flash memory 147 and 512 KB DRAM 148 are integrated in a singlecontroller ASIC. Analog RF components (RF circuit 155 and RF resonatorsand inductors 156) are provided in the separate RF chip.

The image sensor is a CCD or CMOS image sensor. Depending on taggingscheme, it has a size ranging from about 100×100 pixels to 200×200pixels. Many miniature CMOS image sensors are commercially available,including the National Semiconductor LM9630.

The controller ASIC 134 enters a quiescent state after a period ofinactivity when the pen 101 is not in contact with a surface. Itincorporates a dedicated circuit 150 which monitors the force sensorphotodiode 144 and wakes up the controller 134 via the power manager 151on a pen-down event.

The radio transceiver communicates in the unlicensed 900 MHz bandnormally used by cordless telephones, or alternatively in the unlicensed2.4 GHz industrial, scientific and medical (ISM) band, and usesfrequency hopping and collision detection to provide interference-freecommunication.

In an alternative embodiment, the pen incorporates an Infrared DataAssociation (IrDA) interface for short-range communication with a basestation or netpage printer.

In a further embodiment, the pen 101 includes a pair of orthogonalaccelerometers mounted in the normal plane of the pen 101 axis. Theaccelerometers 190 are shown in FIGS. 7 and 8 in ghost outline.

The provision of the accelerometers enables this embodiment of the pen101 to sense motion without reference to surface location tags, allowingthe location tags to be sampled at a lower rate. Each location tag IDcan then identify an object of interest rather than a position on thesurface. For example, if the object is a user interface input element(e.g. a command button), then the tag ID of each location tag within thearea of the input element can directly identify the input element.

The acceleration measured by the accelerometers in each of the x and ydirections is integrated with respect to time to produce aninstantaneous velocity and position.

Since the starting position of the stroke is not known, only relativepositions within a stroke are calculated. Although position integrationaccumulates errors in the sensed acceleration, accelerometers typicallyhave high resolution, and the time duration of a stroke, over whicherrors accumulate, is short.

3 Netpage Printer Description 3.1 Printer Mechanics

The vertically-mounted netpage wallprinter 601 is shown fully assembledin FIG. 9. It prints netpages on Letter/A4 sized media using duplexed8½″ Memjet™ print engines 602 and 603, as shown in FIGS. 10 and 10 a. Ituses a straight paper path with the paper 604 passing through theduplexed print engines 602 and 603 which print both sides of a sheetsimultaneously, in full color and with full bleed.

An integral binding assembly 605 applies a strip of glue along one edgeof each printed sheet, allowing it to adhere to the previous sheet whenpressed against it. This creates a final bound document 618 which canrange in thickness from one sheet to several hundred sheets.

The replaceable ink cartridge 627, shown in FIG. 12 coupled with theduplexed print engines, has bladders or chambers for storing fixative,adhesive, and cyan, magenta, yellow, black and infrared inks. Thecartridge also contains a micro air filter in a base molding. The microair filter interfaces with an air pump 638 inside the printer via a hose639. This provides filtered air to the printheads to prevent ingress ofmicro particles into the Memjet™ printheads 350 which might otherwiseclog the printhead nozzles. By incorporating the air filter within thecartridge, the operational life of the filter is effectively linked tothe life of the cartridge. The ink cartridge is a fully recyclableproduct with a capacity for printing and gluing 3000 pages (1500sheets).

Referring to FIG. 10, the motorized media pick-up roller assembly 626pushes the top sheet directly from the media tray past a paper sensor onthe first print engine 602 into the duplexed Memjet™ printhead assembly.The two Memjet™ print engines 602 and 603 are mounted in an opposingin-line sequential configuration along the straight paper path. Thepaper 604 is drawn into the first print engine 602 by integral, poweredpick-up rollers 626. The position and size of the paper 604 is sensedand full bleed printing commences. Fixative is printed simultaneously toaid drying in the shortest possible time.

The paper exits the first Memjet™ print engine 602 through a set ofpowered exit spike wheels (aligned along the straight paper path), whichact against a rubberized roller. These spike wheels contact the ‘wet’printed surface and continue to feed the sheet 604 into the secondMemjet™ print engine 603.

Referring to FIGS. 10 and 10 a, the paper 604 passes from the duplexedprint engines 602 and 603 into the binder assembly 605. The printed pagepasses between a powered spike wheel axle 670 with a fibrous supportroller and another movable axle with spike wheels and a momentary actionglue wheel. The movable axle/glue assembly 673 is mounted to a metalsupport bracket and it is transported forward to interface with thepowered axle 670 via gears by action of a camshaft. A separate motorpowers this camshaft.

The glue wheel assembly 673 consists of a partially hollow axle 679 witha rotating coupling for the glue supply hose 641 from the ink cartridge627. This axle 679 connects to a glue wheel, which absorbs adhesive bycapillary action through radial holes. A molded housing 682 surroundsthe glue wheel, with an opening at the front. Pivoting side moldings andsprung outer doors are attached to the metal bracket and hinge outsideways when the rest of the assembly 673 is thrust forward. Thisaction exposes the glue wheel through the front of the molded housing682. Tension springs close the assembly and effectively cap the gluewheel during periods of inactivity.

As the sheet 604 passes into the glue wheel assembly 673, adhesive isapplied to one vertical edge on the front side (apart from the firstsheet of a document) as it is transported down into the binding assembly605.

4. Product Tagging

Automatic identification refers to the use of technologies such as barcodes, magnetic stripe cards, smartcards, and RF transponders, to(semi-)automatically identify objects to data processing systems withoutmanual keying.

For the purposes of automatic identification, a product item is commonlyidentified by a 12-digit Universal Product Code (UPC), encodedmachine-readably in the form of a printed bar code. The most common UPCnumbering system incorporates a 5-digit manufacturer number and a5-digit item number. Because of its limited precision, a UPC is used toidentify a class of product rather than an individual product item. TheUniform Code Council and EAN International define and administer the UPCand related codes as subsets of the 14-digit Global Trade Item Number(GTIN).

Within supply chain management, there is considerable interest inexpanding or replacing the UPC scheme to allow individual product itemsto be uniquely identified and thereby tracked. Individual item taggingcan reduce “shrinkage” due to lost, stolen or spoiled goods, improve theefficiency of demand-driven manufacturing and supply, facilitate theprofiling of product usage, and improve the customer experience.

There are two main contenders for individual item tagging: optical tagsin the form of so-called two-dimensional bar codes, and radio frequencyidentification (RFID) tags. For a detailed description of RFID tags,refer to Klaus Finkenzeller, RFID Handbook, John Wiley & Son (1999), thecontents of which are herein incorporated by cross-reference. Opticaltags have the advantage of being inexpensive, but require opticalline-of-sight for reading. RFID tags have the advantage of supportingomnidirectional reading, but are comparatively expensive. The presenceof metal or liquid can seriously interfere with RFID tag performance,undermining the omnidirectional reading advantage. Passive(reader-powered) RFID tags are projected to be priced at 10 cents eachin multi-million quantities by the end of 2003, and at 5 cents each soonthereafter, but this still falls short of the sub-one-cent industrytarget for low-price items such as grocery. The read-only nature of mostoptical tags has also been cited as a disadvantage, since status changescannot be written to a tag as an item progresses through the supplychain. However, this disadvantage is mitigated by the fact that aread-only tag can refer to information maintained dynamically on anetwork.

The Massachusetts Institute of Technology (MIT) Auto-ID Center hasdeveloped a standard for a 96-bit Electronic Product Code (EPC), coupledwith an Internet-based Object Name Service (ONS) and a Product MarkupLanguage (PML). Once an EPC is scanned or otherwise obtained, it is usedto look up, possibly via the ONS, matching product information portablyencoded in PML. The EPC consists of an 8-bit header, a 28-bit EPCmanager, a 24-bit object class, and a 36-bit serial number. For adetailed description of the EPC, refer to Brock, D. L., The ElectronicProduct Code (EPC), MIT Auto-ID Center (January 2001), the contents ofwhich are herein incorporated by cross-reference. The Auto-ID Center hasdefined a mapping of the GTIN onto the EPC to demonstrate compatibilitybetween the EPC and current practices Brock, D. L., Integrating theElectronic Product Code (EPC) and the Global Trade Item Number (GTIN),MIT Auto-ID Center (November 2001), the contents of which are hereinincorporated by cross-reference. The EPC is administered by EPCglobal,an EAN-UCC joint venture.

EPCs are technology-neutral and can be encoded and carried in manyforms. The Auto-ID Center strongly advocates the use of low-cost passiveRFID tags to carry EPCs, and has defined a 64-bit version of the EPC toallow the cost of RFID tags to be minimized in the short term. Fordetailed description of low-cost RFID tag characteristics, refer toSarma, S., Towards the 5c Tag, MIT Auto-ID Center (November 2001), thecontents of which are herein incorporated by cross-reference. For adescription of a commercially-available low-cost passive RFID tag, referto 915 MHz RFID Tag, Alien Technology (2002), the contents of which areherein incorporated by cross-reference. For detailed description of the64-bit EPC, refer to Brock, D. L., The Compact Electronic Product Code,MIT Auto-ID Center (November 2001), the contents of which are hereinincorporated by cross-reference.

EPCs are intended not just for unique item-level tagging and tracking,but also for case-level and pallet-level tagging, and for tagging ofother logistic units of shipping and transportation such as containersand trucks. The distributed PML database records dynamic relationshipsbetween items and higher-level containers in the packaging, shipping andtransportation hierarchy.

4.1 Omnitagging in the Supply Chain

Using an invisible (e.g. infrared) tagging scheme to uniquely identify aproduct item has the significant advantage that it allows the entiresurface of a product to be tagged, or a significant portion thereof,without impinging on the graphic design of the product's packaging orlabelling. If the entire product surface is tagged, then the orientationof the product doesn't affect its ability to be scanned, i.e. asignificant part of the line-of-sight disadvantage of a visible bar codeis eliminated. Furthermore, since the tags are small and massivelyreplicated, label damage no longer prevents scanning.

Omnitagging, then, consists of covering a large proportion of thesurface of a product item with optically-readable invisible tags. Eachomnitag uniquely identifies the product item on which it appears. Theomnitag may directly encode the product code (e.g. EPC) of the item, ormay encode a surrogate ID which in turn identifies the product code viaa database lookup. Each omnitag also optionally identifies its ownposition on the surface of the product item, to provide the downstreamconsumer benefits of netpage interactivity described earlier.

Omnitags are applied during product manufacture and/or packaging usingdigital printers. These may be add-on infrared printers which print theomnitags after the text and graphics have been printed by other means,or integrated color and infrared printers which print the omnitags, textand graphics simultaneously. Digitally-printed text and graphics mayinclude everything on the label or packaging, or may consist only of thevariable portions, with other portions still printed by other means.

4.2 Omnitagging

As shown in FIG. 13, a product's unique item ID 215 may be seen as aspecial kind of unique object ID 210. The Electronic Product Code (EPC)220 is one emerging standard for an item ID. An item ID typicallyconsists of a product ID 214 and a serial number 213. The product IDidentifies a class of product, while the serial number identifies aparticular instance of that class, i.e. an individual product item. Theproduct ID in turn typically consists of a manufacturer number 211 and aproduct class number 212. The best-known product ID is the EAN.UCCUniversal Product Code (UPC) 221 and its variants.

As shown in FIG. 14, an omnitag 202 encodes a page ID (or region ID) 50and a two-dimensional (2D) position 86. The region ID identifies thesurface region containing the tag, and the position identifies the tag'sposition within the two-dimensional region. Since the surface inquestion is the surface of a physical product item 201, it is useful todefine a one-to-one mapping between the region ID and the unique objectID 210, and more specifically the item ID 215, of the product item.Note, however, that the mapping can be many-to-one without compromisingthe utility of the omnitag. For example, each panel of a product item'spackaging could have a different region ID 50. Conversely, the omnitagmay directly encode the item ID, in which case the region ID containsthe item ID, suitably prefixed to decouple item ID allocation fromgeneral netpage region ID allocation. Note that the region ID uniquelydistinguishes the corresponding surface region from all other surfaceregions identified within the global netpage system.

The item ID 215 is preferably the EPC 220 proposed by the Auto-IDCenter, since this provides direct compatibility between omnitags andEPC-carrying RFID tags.

In FIG. 14 the position 86 is shown as optional. This is to indicatethat much of the utility of the omnitag in the supply chain derives fromthe region ID 50, and the position may be omitted if not desired for aparticular product.

For interoperability with the netpage system, an omnitag 202 is anetpage tag 4, i.e. it has the logical structure, physical layout andsemantics of a netpage tag.

When a netpage sensing device such as the netpage pen 101 images anddecodes an omnitag, it uses the position and orientation of the tag inits field of view and combines this with the position encoded in the tagto compute its own position relative to the tag. As the sensing deviceis moved relative to a Hyperlabelled surface region, it is thereby ableto track its own motion relative to the region and generate a set oftimestamped position samples representative of its time-varying path.When the sensing device is a pen, then the path consists of a sequenceof strokes, with each stroke starting when the pen makes contact withthe surface, and ending when the pen breaks contact with the surface.

When a stroke is forwarded to the page server 10 responsible for theregion ID, the server retrieves a description of the region keyed byregion ID, and interprets the stroke in relation to the description. Forexample, if the description includes a hyperlink and the strokeintersects the zone of the hyperlink, then the server may interpret thestroke as a designation of the hyperlink and activate the hyperlink.

4.3 Omnitag Printing

An omnitag printer is a digital printer which prints omnitags onto thelabel, packaging or actual surface of a product before, during or afterproduct manufacture and/or assembly. It is a special case of a netpageprinter 601. It is capable of printing a continuous pattern of omnitagsonto a surface, typically using a near-infrared-absorptive ink. Inhigh-speed environments, the printer includes hardware which acceleratestag rendering. This typically includes real-time Reed-Solomon encodingof variable tag data such as tag position, and real-time template-basedrendering of the actual tag pattern at the dot resolution of theprinthead.

The printer may be an add-on infrared printer which prints the omnitagsafter text and graphics have been printed by other means, or anintegrated color and infrared printer which prints the omnitags, textand graphics simultaneously. Digitally-printed text and graphics mayinclude everything on the label or packaging, or may consist only of thevariable portions, with other portions still printed by other means.Thus an omnitag printer with an infrared and black printing capabilitycan displace an existing digital printer used for variable dataprinting, such as a conventional thermal transfer or inkjet printer.

For the purposes of the following discussion, any reference to printingonto an item label is intended to include printing onto the itempackaging in general, or directly onto the item surface. Furthermore,any reference to an item ID 215 is intended to include a region ID 50(or collection of per-panel region ids), or a component thereof.

The printer is typically controlled by a host computer, which suppliesthe printer with fixed and/or variable text and graphics as well as itemids for inclusion in the omnitags. The host may provide real-timecontrol over the printer, whereby it provides the printer with data inreal time as printing proceeds. As an optimisation, the host may providethe printer with fixed data before printing begins, and only providevariable data in real time. The printer may also be capable ofgenerating per-item variable data based on parameters provided by thehost. For example, the host may provide the printer with a base item IDprior to printing, and the printer may simply increment the base item IDto generate successive item ids. Alternatively, memory in the inkcartridge or other storage medium inserted into the printer may providea source of unique item ids, in which case the printer reports theassignment of items ids to the host computer for recording by the host.

Alternatively still, the printer may be capable of reading apre-existing item ID from the label onto which the omnitags are beingprinted, assuming the unique ID has been applied in some form to thelabel during a previous manufacturing step. For example, the item ID mayalready be present in the form of a visible 2D bar code, or encoded inan RFID tag. In the former case the printer can include an optical barcode scanner. In the latter case it can include an RFID reader.

The printer may also be capable of rendering the item ID in other forms.For example, it may be capable of printing the item ID in the form of a2D bar code, or of printing the product ID component of the item ID inthe form of a 1D bar code, or of writing the item ID to a writable orwrite-once RFID tag.

4.4 Omnitag Scanning

Item information typically flows to the product server in response tosituated scan events, e.g. when an item is scanned into inventory ondelivery; when the item is placed on a retail shelf; and when the itemis scanned at point of sale. Both fixed and hand-held scanners may beused to scan omnitagged product items, using both laser-based 2Dscanning and 2D image-sensor-based scanning, using similar or the sametechniques as employed in the netpage pen.

As shown in FIG. 16, both a fixed scanner 254 and a hand-held scanner252 communicate scan data to the product server 251. The product servermay in turn communicate product item event data to a peer product server(not shown), or to a product application server 250, which may implementsharing of data with related product servers. For example, stockmovements within a retail store may be recorded locally on the retailstore's product server, but the manufacturer's product server may benotified once a product item is sold.

4.5 Omnitag-Based Netpage Interactions

A product item whose labelling, packaging or actual surface has beenomnitagged provides the same level of interactivity as any othernetpage.

There is a strong case to be made for netpage-compatible producttagging. Netpage turns any printed surface into a finely differentiatedgraphical user interface akin to a Web page, and there are manyapplications which map nicely onto the surface of a product. Theseapplications include obtaining product information of various kinds(nutritional information; cooking instructions; recipes; relatedproducts; use-by dates; servicing instructions; recall notices); playinggames; entering competitions; managing ownership (registration; query,such as in the case of stolen goods; transfer); providing productfeedback; messaging; and indirect device control. If, on the other hand,the product tagging is undifferentiated, such as in the case of anundifferentiated 2D barcOde or RFID-carried item ID, then the burden ofinformation navigation is transferred to the information deliverydevice, which may significantly increase the complexity of the userexperience or the required sophistication of the delivery device userinterface.

The invention will now be described with reference to the followingexamples. However, it will of course be appreciated that this inventionmay be embodied in many other forms without departing from the scope ofthe invention, as defined in the accompanying claims.

EXAMPLES Example 1 Preparation of HydroxygalliumNaphthalocyaninetetrasulfonic Acid 4

(i) Gallium(III) chloride (5.70 g; 0.032 mol) was dissolved in anhydroustoluene (68 mL) under a slow stream of nitrogen and then the resultingsolution was cooled in ice/water. Sodium methoxide (25% in methanol;23.4 mL) was added slowly with stirring causing a thick whiteprecipitate to form. Upon completion of the addition, the mixture wasstirred at room temperature for 1 h and thennaphthalene-2,3-dicarbonitrile (22.8 g; 0.128 mol) was addedportionwise, followed by triethylene glycol monomethyl ether (65 mL).The thick slurry was distilled for 2 h to remove the methanol andtoluene. Once the toluene had distilled off, the reaction mixture becamehomogeneous and less viscous and stirred readily. Heating was continuedfor 3 h at 190° C. (internal). The brown/black reaction mixture wascooled to 60° C., diluted with chloroform (150 mL), and filtered undergravity through a sintered glass funnel. The solid residue was washedwith more chloroform (50 mL) and then a further portion (50 mL) withsuction under reduced pressure. The resulting dark green solid was thensequentially washed under reduced pressure with acetone (2×50 mL), DMF(2×50 mL), water (2×50 mL), acetone (2×50 mL), and diethyl ether (2×50mL). The moist solid was air-dried to a dry powder and then heated underhigh vacuum at ca. 100° C. for 1 h to complete the drying process.Naphthalocyaninatogallium methoxytriethyleneoxide 3 was obtained as afine dark green powder (23.14 g; 80%), λ_(max) (NMP) 770 nm.

(ii) Naphthalocyaninatogallium methoxytriethyleneoxide 3 (9.38 g; 0.010mol) was treated with 30% oleum (47 mL) by slow addition via a droppingfunnel while cooling in an ice/water bath under a nitrogen atmosphere.Upon completion of the addition, the reaction mixture was transferred toa preheated water bath at 55° C. and stirred at this temperature for 2 hduring which time the mixture became a homogeneous viscous dark bluesolution. The stirred reaction mixture was cooled in an ice/water bathand then 2-propanol (40 mL) was added slowly via a dropping funnel. Thismixture was then poured into 2-propanol (100 mL) using more 2-propanol(160 mL) to wash out the residues from the reaction flask. Diethyl ether(100 mL) was then added to the mixture which was then transferred to asintered glass funnel and filtered under gravity affording a moist darkbrown solid and a yellow/brown filtrate. The solid was washedsequentially with ether (50 mL), acetone/ether (1:1, 100 mL), and ether(100 mL) with suction under reduced pressure. The resulting solid (13.4g) after drying under high vacuum was then stirred in ethanol/ether(1:3, 100 mL) for 3 days and then filtered and dried to give thetetrasulfonic acid 4 as a fine red/brown solid (12.2 g; 105% oftheoretical yield; 90% purity according to potentiometric titration). ¹HNMR (d₆-DMSO) δ 7.97, 8.00 (4H, dd, J_(7,8)=J_(7,6)=7.2 Hz, H7); 8.49(4H, dd, J_(8,7)=7.2, J_(8,1)=5.7 Hz, H8); 8.84, 8.98 (4H, d,J_(6,7)=7.2 Hz, H6); 10.10, 10.19, 10.25 (4H, d, J_(1,8)=5.7 Hz, H1);11.13, 11.16 (4H, s, H4).

Example 2 Preparation of Ammonium Salts

The following salts were prepared as described below.

(a) Tetrapyridinium 5

Hydroxygallium naphthalocyaninetetrasulfonic acid 4 (189 mg; 0.17 mmol)was suspended in pyridine/water (50:50; 4 mL) and stirred at roomtemperature for 16 h during which time the reaction mixture becamehomogeneous. Ether/ethanol (86:14, 35 mL) was added to precipitate thesalt and the supernatant liquid was decanted off before ether/ethanol(83:17, 12 mL) was added with stirring. The solid was filtered off andwashed with ether/ethanol (50:50, 2×5 mL) and ether (2×5 mL). Afterdrying under high vacuum, the tetrapyridinium salt 5 was obtained as agreen powder (136 mg; 56%). ¹H NMR (d₆-DMSO) δ 7.78 (8H, dd, J=6.3, 6.3Hz, H3′, H5′); 7.97, 8.00 (4H, dd, J_(7,8)=J_(7,6)=7.2 Hz, H7); 8.25(4H, dd, J=7.8, 7.8 Hz, H4′); 8.49 (4H, dd, J_(8,7)=7.2, J_(8,1)=5.7 Hz,H8); 8.80 (8H, d, J=7.8 Hz, H2′, H6′); 8.84, 8.98 (4H, d, J_(6,7)=7.2Hz, H6); 10.10, 10.19, 10.25 (4H, d, J_(1,8)=5.7 Hz, H1); 11.13, 11.16(4H, s, H4).

(b) Tetrakis(1,8-diazabicyclo[5.4.0]undec-7-enium) 9 Comparative Example

Hydroxygallium naphthalocyaninetetrasulfonic acid 4 (348 mg; 0.31 mmol)and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (306 mg; 2.17 mmol) werestirred in methanol (5 mL) for 20 h at room temperature during whichtime the reaction mixture became homogeneous. The mixture was dilutedwith ethanol/ether (25:75; 20 mL) and stirred for 30 min. Thesupernatant was decanted off, ether (20 mL) was added and the solid wasfiltered off, washing with ethanol/ether (50:50; 2×20 mL), and ether(2×20 mL). The tetraammonium salt 9 was obtained as a green powder afterdrying under high vacuum (252 mg; 48%). ¹H NMR (d₆-DMSO) δ 1.1-1.2 (32H,m, H3′, H4′, H5′, H10′); 2.5 (8H, m, H6′); 3.0-3.1 (24H, m, H2′, H9′,H11′); 7.97, 8.00 (4H, dd, J_(7,8)=J_(7,6)=7.2 Hz, H7); 8.49 (4H, dd,J_(8,7)=7.2, J_(8,1)=5.7 Hz, H8); 8.84, 8.98 (4H, d, J_(6,7)=7.2 Hz,H6); 10.10, 10.19, 10.25 (4H, d; J₁₈=5.7 Hz, H1); 11.13, 11.16 (4H, s,H4).

(c) Tetrakis(tributylammonium) 8 Comparative Example

Hydroxygallium naphthalocyaninetetrasulfonic acid 4 (905 mg; 0.81 mmol)and tributylamine (2.32 mL; 9.70 mmol) were stirred in ethanol (96%; 5mL) for 4.75 h at room temperature during which time the reactionmixture became homogeneous. The solution was diluted with ether (100 mL)and the precipitated solid was filtered off, washing with more ether(2×25 mL). Excess amine was removed by stirring the solid intetrahydrofuran/ether (70:30, 40 mL) for 2 h and filtering off thesolid. The tetrakis(tributylammonium) salt 8 was dried under high vacuumand obtained as a green powder (730 mg; 49%). This salt is sparinglysoluble in water but readily dissolves in ethanol. ¹H NMR (d₆-DMSO) δ0.90 (12H, t, J=7.2 Hz, H4′); 1.34 (8H, sxt, J=7.5 Hz, H3′); 1.58 (6H,m, H2′); 3.03 (6H, br dd, J=7.8, 7.8 Hz, H1′); 7.97, 8.00 (4H, dd,J_(7,8)=J_(7,6)=7.2 Hz, H7); 8.49 (4H, dd, J_(8,7)=7.2, J_(8,1)=5.7 Hz,H8); 8.84, 8.98 (4H, d, J_(6,7)=7.2 Hz, H6); 10.10, 10.19, 10.25 (4H, d,J_(1,8)=5.7 Hz, H1); 11.13, 11.16 (4H, s, H4).

(d) Tetraimidazolium 7

Hydroxygallium naphthalocyaninetetrasulfonic acid 4 (1.40 g; 1.25 mmol)and imidazole (0.596 g; 8.75 mmol) were suspended in methanol/water(80:20; 17.5 mL) and then the resulting green mixture was stirred atroom temperature for 2 h, becoming homogeneous after 1 h. The solutionwas diluted with diethyl ether (50 mL), stirred for 15 min. and thenallowed to stand. The supernatant liquid was decanted off and thenether/methanol (50:50; 20 mL) was added with stirring. The solid wasfiltered off, washing with ether/methanol (50:50; 3×20 mL) and ether(2×20 mL). The solid was then suspended in methanol/ether (50:50; 20 mL)and stirred for 3 h. Filtration and drying under high vacuum affordedthe tetraimidazolium salt 7 as a green powder (1.32 g; 76%). ¹H NMR(d₆-DMSO) δ 7.61 (8H, br s, H4′, H5′); 7.98, 8.02 (4H, dd,J_(7,8)=J_(7,6)=7.2 Hz, H7); 8.49 (4H, br m, H8); 8.84, 8.98 (4H, d,J_(6,7)=7.2 Hz, H6); 8.91 (4H, br s, H2′); 10.10, 10.19, 10.25 (4H, d,J_(1,8)=5.7 Hz, H1); 11.13, (4H, br m, H4).

Example 3 Preparation of Inks and Reflectance Spectra of Ammonium Salts

A solution of each salt was made up in an ink vehicle according to Table1.

TABLE 1 Composition of dyeless ink vehicles for salt derivatives VehicleVehicle Vehicle component A (% w/v) B (% w/v) C (% w/v) Ethylene glycol6 5.45 5.45 Diethylene glycol 2 1.82 1.82 2-pyrrolidinone 5 4.55 4.55Glycerol 4.5 4.09 4.09 Urea 7 6.36 6.36 Surfynol (5EO/OH) 0.5 0.45 0.451,3-propanediol — 9.00 — ethanol — — 9.00 Water 75 68.18 68.18

The resulting clear green solutions were printed on Celcast mattphotoquality inkjet paper (143 gsm) on an Epson C61 inkjet printer andthen the reflectance spectra were measured on a Cary 5 UV-visspectrophotometer. Results are given in Table 2.

TABLE 2 Relationship between amine component of tetrasulfonate salts, pHof ink made according to Table 1, and position of Q-band Ink vehicleCom- (concentra- Amine Amine: Q-band Example pound tion, mM) (B) 4pK_(a) pH (λ_(max)) 4 C (2) none — — 2.8 805 nm 3(a) 5 B (1.36) Pyridine4:1 5.2 4.6 807 nm 3(d) 7 B (1.5) Imidazole 4:1 6.8 6.1 803 nm^(a) 3(c)8 C (2) Bu₃N 4:1 ca. 6.8 792 nm 3(b) 9 A (2) DBU 4:1 11 7.7 744, ca. 787nm^(b) 12 ^(a)Figure 28; ^(b)Figure 29

From Table 2, it can be seen that compounds 5, and 7, where BH⁺ has apK_(a) in the range of 4 to 9 and the pH of the ink formulation isbetween 4 and 6.5, the Q-band of absorption is greater than 800 nm.However, for compounds 8 and 9, where BH⁺ has a pK_(a) greater than 9and the pH of the ink formulation is greater than 6.5, the Q-band issignificantly less than 800 nm. Accordingly, compounds 5, and 7 aresuitable for formulating inks which are not too acidic to be compatiblewith conventional CMYK inks, and which retain strong absorption in thenear-IR region above 800 nm.

Other amine salts of the gallium naphthalocyanine tetrasulfonate 4 wereprepared analogously to those prepared above in Examples 2(a)-(d), andformulated as 2 mM solutions in ink vehicle A. The resulting clear greensolutions were printed on Celcast matt photoquality inkjet paper (143gsm) on an Epson C61 inkjet printer and then the reflectance spectrawere measured on a Cary 5 UV-vis spectrophotometer. Results are given inTable 3.

TABLE 3 Spectroscopic properties of other ammonium salts Ink Q-bandExample Amine (B) Amine:1 vehicle (λ_(max)) 3(e)1,4-diazabicyclo[2.2.2]octane (DABCO) 4:1 A 802 nm 3(f) Triethanolamine4:1 A 794 nm 3(g) Piperazine 4:1 A 794 nm 3(h) Glucosamine 4:1 A 798,740 3(i) Tributylamine 1:1 A nm 3(j) 2-(2′-hydroxyethoxy)ethanolamine4:1 A 805 nm 3(k) Quinoline 4:1 A 794, 738 3(l) Triethylamine 4:1 A nm803 nm 795 nm

From Table 3, it can be seen that DABCO and quinoline in astoichiometric ratio of 4:1 provide salts, which can be formulated intoinks having acceptable reflectance spectra. Stronger bases used in thesame ratio are generally unsuitable and result in a significantblue-shift. However, the use of fewer equivalents of a stronger base canstill provide inks having red-shifted Q-bands. Example 3(i) usestributylamine in a ratio of 1:1 and provides a formulation having aQ-band at 805 nm. By contrast, tributylamine in a ratio of 4:1 (Table 2)provides a formulation having a blue-shifted Q-band at 792 nm.

Example 4 Preparation and Reflectance Spectra of Inks With AddedCarboxylate Salts

Inks according to the present invention may also be prepared withoutisolation of the naphthalocyanine salts. For example, the tetrasulfonicacid 4 may be formulated in an ink vehicle and the pH adjusted using asuitable base or buffer. Examples 4(a) and 4(b) below describe thepreparation of inks by addition of carboxylate salts in an inkcomprising the tetrasulfonic 4.

(a) Lithium/Sodium Acetate and Tetrasulfonic Acid 4

The tetrasulfonic acid 4 was made up to 2 mM in ink vehicle B containing8 mM NaOAc or LiOAc. This gave a clear green solution containing 6 (pH5.1) that was printed on Celcast matt photoquality inkjet paper (143gsm). The reflectance spectrum had λ_(max) 806 nm for both sodium andlithium.

(b) EDTA Disodium Salt and Tetrasulfonic Acid 4

The tetrasulfonic acid 4 was made up to 1.5 mM in ink vehicle Bcontaining 3 mM ethylenediaminetetraacetic acid (EDTA) disodium salt.This gave a clear green solution (pH 3.7) that was printed on Celcastmatt photoquality inkjet paper (143 gsm). The reflectance spectrum hadλ_(max) 805 nm.

Example 5 Preparation and Reflectance Spectra of Inks Comprising MixedSalts

Inks according to the present invention may also comprise mixed salts.Mixed salts may be advantageous in providing a suitable balance ofproperties or for tuning the spectroscopic characteristics of a salt.For example, in Example 5(b) the direct addition of three equivalents ofp-toluenesulfonic acid to the tetrakis(DBUammonium) salt 9 in the inkformulation lowers the pH from 7.7 to 4.0 and shifts the Q-band to 806nm indicating that protonation of the internal meso-nitrogens has takenplace.

(a) Tetrasulfonic Acid 4 and Tetrakis(Tributylammonium) Salt 8

Solutions of the tetrasulfonic acid 4 and the tetrakis(tributylammonium)salt 8 (2 mM in vehicle C) were mixed in the ratios as shown in Table 4.The resulting clear green solutions were printed on Celcast mattphotoquality inkjet paper (143 gsm) with an Epson C61 inkjet printer andthe pH and maximum absorptions were measured.

TABLE 4 Properties of mixed tetrasulfonic acid 4 and thetetrakis(tributylammonium) salt 8 in vehicle C Tetrasulfonic acid4/tetrakis(tributylammonium) salt 8 pH Q-band (λ_(max)) 1:3 3.6 796 nm3:1 2.9 807 nm(b) Tetrakis(DBUammonium) Salt 9 and p-Toluenesulfonic Acid

The DBUammonium salt 9 (26.3 mg; 15.2 μmol) and p-toluenesulfonic acid(8.68 mg; 45.6 μmol) were dissolved in ink vehicle B (11.2 mL) to makeup a solution that was 1.36 mM with respect to the naphthalocyanine.This gave a clear green solution (pH 4.0) that was printed on Celcastmatt photoquality inkjet paper (143 gsm). The reflectance spectrum hadλ_(max) 806 nm (FIG. 30).

(c) Imidazolium Salt 7 and Acetic Acid

The tetraimidazolium salt 7 was made up to 1.5 mM in ink vehicle Bcontaining 3 mM acetic acid. This gave a clear green solution (pH 5.1)that was printed on Celcast matt photoquality inkjet paper (143 gsm).The reflectance spectrum had λ_(max) 807 nm (FIG. 31).

Example 6 Lightfastness

An Osram 250 W metal halide lamp (HQI-EP 250 W/D E40) with an intensityof 17,000 lumens, (approximately 70,000 lux) was used to irradiateprinted samples positioned at a distance of 9.0 cm from the globe. Theindustry standard measurement of lightfastness is the time taken for asample to fade by 30% under typical indoor lighting conditions. Typicalindoor lighting conditions are defined as illumination under a lightingintensity of 500 lux for 10 hours per day.

$\begin{matrix}{{Lightfastness} = {{Time}\mspace{14mu} {taken}\mspace{14mu} {to}\mspace{14mu} {fade}{\mspace{11mu} \;}{by}\mspace{14mu} 30\% \times}} \\{{\left( {70,000\mspace{14mu} {{lux}/500}\mspace{14mu} {lux}} \right) \times \left( {24\mspace{11mu} h\text{/}10\mspace{14mu} h} \right)}} \\{= {{Time}\mspace{14mu} {taken}\mspace{14mu} {to}\mspace{14mu} {fade}{\mspace{11mu} \;}{by}\mspace{14mu} 30\% \times 336}}\end{matrix}$

TABLE 5 Projected lifetimes of ammonium salts printed on paper.Concentration in ink pH of Lifetime Galliumnaphthalocyaninetetrasulfonate salt vehicle (A or B) (mM) ink (years)Tetrapyridinium 5 1.5 (A) 4.6 31 Tetraimidazolium 7 1.5 (B) 6.1 38.5Tetraimidazolium 7/acetic acid (2 equiv) 1.5 (B) 5.1 38.5 Tetrasulfonicacid 4/lithium acetate (4 equiv)  2 (B) 5.1 37.3 Tetrasulfonic acid4/sodium acetate (4 equiv)  2 (B) 5.1 36.5 Tetrasulfonic acid 4/lithiumacetate (4 equiv) 1.5 (B) 5.1 22.7 Tetrasulfonic acid 4/sodium acetate(4 equiv) 1.5 (B) 5.1 21.9 Tetrakis(DBUammonium) 9  2 (A) 7.7 7.9Tetrakis(DBUammonium) 9/p-TsOH (3 equiv) 1.36 (B)  4.0 17.5Tetrakis(tributylammonium) 8  2 (B) 6.8 35.3

All inks according to the present invention, with a pH in the range of3.5 to 7, have excellent lightfastness. By contrast, the ink preparedfrom tetrakis(DBUammonium) 9, having a pH of 7.7, had poor lightfastnesswith a projected lifetime of only 7.9 years.

This surprising result is a further advantage of the present inventionand is understood to be a result of the protonated macrocycle being lessreactive towards singlet oxygen.

Example 7 Ozonefastness

Inks were formulated from a variety of salts using the ink vehicles A,B, C, D, F, H or I. Ink vehicles A-C were described in Table 1 above.Table 6 below describes ink vehicles D, F, H and I.

TABLE 7 Composition of dyeless ink vehicles Component D (% w/v) F (%w/v) H (% w/v) I (% w/v) ethylene glycol 5.45 5.45 5.13 5.22 diethyleneglycol 1.82 1.8  1.71 1.74 2-pyrrolidinone 4.55 4.55 4.27 8.70 glycerol4.09 4.10 3.85 3.91 urea 6.36 — — — surfynol (5EO/OH) 0.45 0.45 0.430.43 1,3-propanediol — 9.10 8.55 8.70 1,2-hexanediol — — 5.98 —1-propanol 9.00 — — — water 74.5  70.1  71.3 

Ozonefastness of inks printed on Celcast matt photoquality inkjet paper(143 gsm) were tested as follows. The printed samples were exposed toozone at a concentration of 1 ppm until the intensity at 810 nm haddecreased to 70%. ‘F’ denotes a final result for samples that hadreached 70% intensity. Other samples had intensity >70% during the testperiod and the ozone lifetime was extrapolated from acquired data.

TABLE 8 Ozonefastness of printed inks Concentration Ozone lifetimeCompound Formulation (mM) pH (y) 9 A 1.36 n/a 1.6 (F) 9 B 1.36 6.8 2.3(F) 9 + 3 eq. TsOH A 1.36 n/a 4.2 (F) 9 + 3 eq. TsOH B 1.36 4.0 4.8 (F)9 A 2.0 7.7 7.7 (F) 5 A 1.5 5.5 1.6 (F) 5 B 1.5 4.6 8.2 (F) 8 C 2.0 6.812.6 (F)  8 C 1.36 7.5 5.5 (F) 8 B 1.36 n/a 7.5 (F) 7 B 1.5 6.1 9.8 (F)7 + 2 eq AcOH B 1.5 5.1 12.2(F)  7 D 1.5 6.6 3.5 (F) 7 F 1.5 n/a 15.8 7I 1.5 n/a 11.1 (F)  7 H 1.5 n/a 13.9 (F)  4 + 4 eq imidazole B 1.5 6.44.5 (F) 4 + 16 eq imidazole B 1.5 7.5 2.8 (F) 6 (Li⁺ salt) B 1.5 5.3 2.3(F)

Inks according to the present invention were shown to have acceptableozonefastness, in addition to acceptable lightfastness.

In conclusion, gallium naphthalocyanine salts and ink formulations ofthe present invention are excellent for use with netpage and Hyperlabel™systems. These dyes and inks exhibit near-IR absorption above 800 nm,good solubility in inkjet ink formulations, negligible or low visibilityand excellent lightfastness. Moreover, these dyes can be prepared in ahigh-yielding, expedient and efficient synthesis.

1. An aqueous formulation comprising a sulfonated water-solubleIR-absorbing naphthalocyanine dye having a central metal atom moiety,wherein a pH of said formulation is in the range of 4 to 6.5 so as tominimize visible coloration of the formulation.
 2. The formulation ofclaim 1, wherein said formulation is buffered.
 3. The formulation ofclaim 1 further comprising at least one base B, wherein a conjugate acidBH⁺ of said at least one base B has a pK_(a) of between 4 and
 9. 4. Theformulation of claim 3, wherein a conjugate acid BH⁺ of said at leastone base B has a pK_(a) of between 4.5 and
 8. 5. The formulation ofclaim 3 comprising a nitrogen base, an oxyanion base or mixturesthereof.
 6. The formulation of claim 5, wherein said nitrogen base is anitrogen-containing C₅₋₁₂ heteroaryl base.
 7. The formulation of claim6, said nitrogen base is imidazole or pyridine.
 8. An inkjet inkcomprising a formulation according to claim
 1. 9. An inkjet inkcomprising a dye according to claim 1, wherein said ink has a λ_(max) of800 nm or more.
 10. A method of minimizing visible coloration of asulfonated water-soluble IR-absorbing naphthalocyanine dye, saidnaphthalocyanine dye comprising a central metal atom moiety, said methodcomprising formulating said naphthalocyanine dye at a pH in the range of4 to 6.5.